setter who has organized many contests. This is never a reason to make a round
unrated. Today, For this reason, the **div1 part of the round is unrated**. Div2 stays rated., unrated**. Div2 stays rated. Sometimes known problems appear in a contest, it
happened to me as
Rating changes for last rounds are temporarily rolled back. They will be returned soon.
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Results
1.
unrated
Last visit:
23 months ago
Registered:
14 years ago
2.
About div1E (round #810) I am the coordinator of Round #810. I will be brief and clear.
The div1E problem was copied by one of the two authors, it was not a coincidence.
For this reason, the **div1 part of the round is unrated**. Div2 stays rated.
Sometimes known problems appear in a contest, it happened to me as an author and to any problem setter who has organized many contests. This is never a reason to make a round unrated.
Today something different happened, the problem was deliberately copied and the author did not tell anything to anybody (not even to the other author). Codeforces (and me personally) condemns this behavior.
A final personal remark: I feel sad. Please future authors: do not copy problems. It's a waste of everyone's time.
Announcement of Codeforces Round 810 (Div. 1)
3.
About the Failed Round 591/Technocup 2020 — Elimination Round 1 Hi Codeforces!
Unfortunately, ill-wishers thwarted the round by making DDOS on our infrastructure. Neither the coordinator nor the writers of the round are subjects to blame for the failure. Please do not downvote the announcement of the round. I think that this situation is an additional reason to support the writers. They worked hard and prepared good problems!
Apparently, such an attack should be regarded as a symptom of the fact that Codeforces outgrew the youth phase and entered serious adult life. Of course, we will respond with adequate measures to protect ourselves from such incidents. Fortunately, for almost 10 years of work, a large community has formed around those who care about Codeforces. We are not worried about possible additional expenses or efforts. We can do this. The rounds must go on.
— [user:MikeMirzayanov,2019-10-06]
**UPD 1:** All three of today's rounds will be unrated.
**UPD 2:** Hooray! Today we've survived another DDOS attack. The round ...
today's rounds will be unrated. **UPD 2:** Hooray! Today we've survived
another DDOS attack. The round, **UPD 1:** All three of today's rounds will be unrated.
4.
Codeforces Round #639 Hello, Codeforces!
I'm very glad to invite you to [contest:1344] and [contest:1345]. This contest will take place on [contest_time:1344]. In both divisions, you will have **2 hours 15 minutes** to solve **6 problems**. The score distribution will be announced closer to the start of the contest.
Of course, this round would not be possible without the help of many people, who I'd like to thank:
- [user:isaf27,2020-05-01], for coordinating this round, and helping with solution ideas.
- My ICPC teammates [user:Kuroni,2020-05-01] and [user:strongoier,2020-05-01], and coach [user:cn355,2020-05-01], for encouraging me to pursue competitive programming. In particular, I'd like to thank [user:Kuroni,2020-05-01] for being so spectacularly bad that a barely-orange user like myself actually has a place on our team.
- [user:300iq,2020-05-01], [user:antontrygubO_o,2020-05-01], [user:Ari,2020-05-01], [user:ffao,2020-05-01], [user:fpc_coder,2020-05-01], [user:gamegame,2020-05-01], [user:Kur...
the long queue and other issues, the contest is unrated. There was also a bug
that gave us trouble, **UPD** Unfortunately due to the long queue and other issues, the contest is
unrated. There was
Announcement of Codeforces Round 639 (Div. 1)
Announcement of Codeforces Round 639 (Div. 2)
5.
Educational Codeforces Round 91 is ruined and unrated Hello.
Unfortunately, the Educational Codeforces Round 91 round will be unrated and, actually, it was completely ruined. I don’t understand what happened yet. At some point in time, all systems began to work unstably and actually stopped working. So far I have no understanding what happened. You may have to change the schedule for future rounds. Sorry. We have such a black stripe.
Very upset and demotivated.
Mike.
Educational Codeforces Round 91 is ruined and unrated, Hello. Unfortunately, the Educational Codeforces Round 91 round will be unrated
and, actually, Unfortunately, the Educational Codeforces Round 91 round will be unrated and,
actually, it was
6.
Goodbye 74TrAkToR + Problem A~E: The problems themselves are good and typical A~E. Indeed I like problem D. The pretest for A is a bit weak, and it's not a big problem yet.
+ Problem F: The problem has an origin. :) See the link: [click](https://www.luogu.com.cn/problem/P9394). The problem in contest is only a weakened version of the one in Luogu.
+ Problem G: It's said that our great coordinator had not proved the time complexity of the intended solution is correct :) If the authors did, please share it in the editorial. (although this problem is completely beyond my ability :) )
+ Problem H: Oh dear [user:74TrAkToR,2023-12-30], could you please OEIS the sequence before you use the "several-integer-input" problem in
rounds next time? Anyone who copied the first example and opened [https://oeis.org/A286331](https://oeis.org/A286331) could quickly get the formula. And the problem itself is not so hard imo. Anyway, it should not be used in contest, especially for the last problem.
For me pers...
I advise making the round unrated.
7.
Educational Codeforces Round 121 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1626] [contest:1626] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2022-01-15] Dalabaev, Vladimir [user:vovuh,2022-01-15] Petrov, Ivan [user:BledDest,2022-01-15] Androsov, Mak...
**UPD:** Unfortunately, the round is unrated. We are sorry for the
inconvenience. You can upsolve
Announcement of Educational Codeforces Round 121 (Rated for Div. 2)
8.
Testing Round #16 (Unrated) Hello, Codeforces!
Paul [user:stingray,2020-05-07] Komkoff is my hero! He found some issues in the network configuration. The most important of them was about flow control auto-negotiation: in case of our network routers the number of dropped packets reduced in times. Thanks!
To be sure that it really helped to fix the issue I ask you to take part in [contest:1351]. It will start on [contest_time:1351]. Probably, it will contain 3 easy problems which are not prepared for now (I'll use some old problems, I think). The only reason to host the round is to check the system under a load. It will be an unrated round.
I am upset about what happened with the last round. Once again, I apologize to both the participants and the writer, coordinator and testers. I wrote [user:Monogon,2020-05-07] about the incident and apologized.
I am sure that the only way to **absolutely** prevent unrated rounds is just don't host them. And this is not my way. The most popular rounds were hosted with...
Testing Round #16 (Unrated), under a load. It will be an unrated round., will be an unrated round. I am upset about what happened with the last round.
Once again, I, I am sure that the only way to **absolutely** prevent unrated rounds is just
don't host them. And
Announcement of Testing Round 16 (Unrated)
9.
About Unrated Educational Codeforces Round 121 Hello, Codeforces.
Unfortunately, we have to declare the round unrated.
Absolutely, these are not issues of the side of Codeforces code, but rather it is a hardware issue. Probably, electricity, power unit or something else. This led to unexpected repeated reboots of the server with the database. I hope that we will be able to quickly deal with this.
We apologize to the writers of the round and its participants.
P.S. Please, do not downvote the round announcement: the writers are not to blame for what happened. And in general, this time it is difficult to blame someone. Sometimes hardware fails.
Mike.
About Unrated Educational Codeforces Round 121, Unfortunately, we have to declare the round unrated.
10.
Petition to revoke unrated account permissions to post comments/blogs Unrated Account Disaster
==================
Recently there have been an obscene number of unrated accounts showing up. Several of them have inappropriate names, so I won't give examples because I want to keep this post clean, but I'm sure you have seen them in the comments. They are likely all by the same individual, possibly with a few copy-cat troublemakers as well.
Recently, certain ones have begun to spam useless comments on old posts to clog up the recent actions, effectively hiding all relevant conversations except on the blog posts they spam on. For whatever reason, these are overwhelmingly on [user:Errichto,2020-07-10]'s old blog posts. Occasionally there are also a flood of obscene blog posts made by the user themselves.
Here's an example of what I mean:
#### This is obnoxious and I would like to see it stop.
The current solution clearly doesn't work. As soon as they get banned or muted or whatever, they c...
Petition to revoke unrated account permissions to post comments/blogs, Recently there have been an obscene number of unrated accounts showing up.
Several of them have, Unrated Account Disaster ==================
11.
Codeforces Round 591 (and Technocup — Elimination Round 1) Hi all!
This weekend, on [contest_time:1223] we will hold Codeforces Round 591. It is based on problems of Technocup 2020 Elimination Round 1 that will be held at the same time.
Technocup is a major olympiad for Russian-speaking high-school students, so if you fall into this category, please register at <a href="https://technocup.mail.ru/">Technocup 2020 website</a> and take part in the Elimination Round.
Div. 1 and Div.2 editions are open and rated for everyone. Register and enjoy the contests!
The Elimination Round authors are [user:BledDest,2019-10-06], [user:MikeMirzayanov,2019-10-06], [user:Ne0n25,2019-10-06], [user:PikMike,2019-10-06], [user:Roms,2019-10-06], [user:adedalic,2019-10-06] and me. This round would also be not possible without the help of our testers: [user:KAN,2019-10-06], [user:chemthan,2019-10-06], [user:gisp_zjz,2019-10-06], [user:Kallaseldor,2019-10-06], [user:JeffreyHo,2019-10-06], [user:danya.smelskiy,2019-10-06], [user:Juve45,2019-10-06], thank you...
Unfortunately, the round is **unrated**.
Announcement of Technocup 2020 - Elimination Round 1
12.
Codeforces Global Round 11 <img src="/predownloaded/2e/e2/2ee2f0f95f05aae6ca6f47812dae2dc2aabf277b.png" style="width:200px; float:right; margin: 0 1em 1em 1em"/>
Hi!
On [contest_time:1427] we will host [contest:1427].
This is the fifth round of the 2020 series of [Codeforces Global Rounds](https://codeforces.com/blog/entry/65002). The rounds are open and rated for everybody.
The prizes for this round are as follows:
- 30 best participants get a t-shirt.
- 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.
The prizes for the 6-round series in 2020:
- In each round top-100 participants get points according to the [table](https://pastebin.com/QT5sXEaT).
- The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
- The best 20 participants over all series get sweatshirts and place certificates.
Thanks to XTX, which in 2020 supported the global rounds initiative!
Problems for this round ar...
because just before the round there will be a 10-minutes-long unrated testing
round. Considering the, -minutes-long unrated testing round. Considering the recent Codeforces
downtime, this is a measure to
Announcement of Codeforces Global Round 11
13.
Codeforces Round #655 (Div. 2) Hey everybody!
We ([user:MagentaCobra,2020-07-05], [user:Tlatoani,2020-07-05], [user:golions,2020-07-05], [user:qlf9,2020-07-05]) are super excited to invite you to take part in [contest:1372], which will happen on [contest_time:1372]. _Please note the unusual start time_. The round is rated for users with rating strictly less than **2100**, although higher rated users are more than welcome to take part out of competition.
Huge thanks to those who helped make this round possible:
- [user:Tlatoani,2020-07-06], [user:golions,2020-07-06], [user:qlf9,2020-07-06] for creating problems and preparation
- [user:antontrygubO_o,2020-07-05] for r̶e̶j̶e̶c̶t̶i̶n̶g̶ ̶m̶o̶s̶t̶ ̶o̶f̶ ̶o̶u̶r̶ ̶p̶r̶o̶b̶l̶e̶m̶s̶ coordinating our round
- [user:gamegame,2020-07-05], [user:dorijanlendvaj,2020-07-05], [user:thenymphsofdelphi,2020-07-05], [user:aryanc403,2020-07-05], [user:Ari,2020-07-05], [user:alireza_kaviani,2020-07-05], [user:KonaeAkira,2020-07-05], [user:Mn619,2020-07-05], [user:AmShZ,2020-07...
will be unrated. We're extremely sorry this happened, and all of us are sad
about it. We hope you will, **UPD:** Due to long queue, the round will be unrated. We're extremely sorry
this happened, and all
14.
About the Round 382 Good afternoon!
I've decided to share my thoughts on the round 382.
Of course, it turned upset not only to me, but also to the round coordinator [user:GlebsHP,2016-11-28].
In this round the main negative feedback were caused by two problems: [problem:735D] and [problem:735C].
Regarding [problem:735D]. I do not share the criticism to this problem. In fact, to solve it would be nice to be familiar with <a href="https://en.wikipedia.org/wiki/Goldbach's_conjecture"> Goldbach's Conjecture</a> and better with <a href="https://en.wikipedia.org/wiki/Prime_number_theorem">Prime Number Theorem</a>. These facts are medium-popular in the world of programming contests. Familiarity with them is useful, gives useful insight into primes. It is important: in this problem it was necessary to perform a simple, but nevertheless, additional step to find solution. It seems to me that it's okay to use problems that have a reduction to some popular and semi-popular topics. Otherwise, it is th...
any argument in favor of unrated round. I personally, would not include it in
my contest. But the, in a round. It can not take a role of any argument in favor of unrated round.
I personally, would not, social networks it does not seem respectful to do to them unrated. I share the
view that it
15.
My thoughts on clarifications and on the round #677. Alright, I'm done. I wanted to write a blog like that for a long time, but now I really don't have enough patience to ignore this issue anymore.
I want to say that I get 100-200 clarifications each Div.3 round. It doesn't even matter how well the statements are, it doesn't matter if there are any issues with solutions or checkers, people always find what to ask.
Before I start whining here, I really want to recommend anyone to read these two [user:Um_nik,2020-10-20] blogs: [this one](https://codeforces.com/blog/entry/62730) and [this one](https://codeforces.com/blog/entry/62744). Sorry, [user:Um_nik,2020-10-20], I unnecessarily tagged you, I will not do that anymore.
Now some breaking news for most participants: _your local IDE compiler_ and _Codeforces compiler_ are **actually** different things! If your code works fine locally but gets WA/TL/RE/ML/etc on Codeforces, it (most probably) means you have a bug somewhere in your code. There are rare cases when the issue is with comp...
**during the time we were figuring out if we really have to make it unrated**.
I got something like, even without direct mentioning): one guy wrote that "this round is complete
disaster make itunrated, make it unrated". I opened his submissions list and saw he solved only A and
B. The only thing that
16.
April Fools Day Contest 2024 Hello, <s>April Fools lovers</s> Codeforces!
We, [user:AlperenT,2024-03-26], [user:flamestorm,2024-03-26], [user:toxicpie9,2024-03-26], and [user:willy108,2024-03-26], would like to invite everyone on Codeforces to [contest:1952]! The 12th April Fools Day Contest will take place on [contest_time:1952]. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
In this round, you will be given $n$ cool bugaboos where $-1 \le n \le \textbf{[REDACTED]}$ and **2** hours to solve them. The contest will use extended ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them). You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise.
Please note that the round is **unrated** and that the penalty for a **wrong submission** is **10** minutes.
To get an idea of what the contest will look like, you can check out the contests of the pas...
Please note that the round is **unrated** and that the penalty for a **wrong
submission** is **10
Announcement of April Fools Day Contest 2024
17.
Codeforces Round #743 Hello Codeforces!
[user:Asymmetry,2021-09-16] and I are glad to invite you to [contest:1572] and [contest:1573], which will be held on [contest_time:1572].
Each division will have **6 problems** and **2 hours** to solve them. All problems were written and prepared by [user:Asymmetry,2021-09-16] and me. The round will be rated for both divisions.
We would like to thank:
- [user:1-gon,2021-09-16] for coordinating the round and helping us with the problems.
- [user:mnbvmar,2021-09-16], [user:gamegame,2021-09-16], [user:dorijanlendvaj,2021-09-16], [user:tnowak,2021-09-16], [user:Jasiekstrz,2021-09-16], [user:ijxjdjd,2021-09-16], [user:shxgun,2021-09-16], [user:lcaonmst,2021-09-16], [user:-_-INV4D3R-_-,2021-09-16], [user:ToxicPie9,2021-09-16], [user:Shinchan01,2021-09-16] and [user:Krzaq,2021-09-16] for testing the round and providing useful feedback.
- [user:ToxicPie9,2021-09-16] for being a VIP tester.
- finally, [user:MikeMirzayanov,2021-09-16] for great platforms Codeforc...
**UPD3:** We are sorry that the round became unrated due to the long queue. We
hope that you, ; $3500$ **UPD3:** We are sorry that the round became unrated due to the long
queue. We hope that
Announcement of Codeforces Round 743 (Div. 1)
Announcement of Codeforces Round 743 (Div. 2)
18.
VK Cup 2017 Round 3 + Codeforces Round #412 -- Tutorial Here is the tutorial of VK Cup 2017 Round 3 and Codeforces Round #412. Enjoy!
<spoiler summary="Is it rated?">
[tutorial:807A]
<spoiler summary="Code">
~~~~~
n = int(input())
results = []
for i in range(n):
results.append(list(map(int, input().split())))
for r in results:
if r[0] != r[1]:
print("rated")
exit()
for i in range(n):
for j in range(i):
if results[i][0] > results[j][0]:
print("unrated")
exit()
print("maybe")
~~~~~
</spoiler>
</spoiler>
<spoiler summary="T-Shirt Hunt">
[tutorial:807B]
<spoiler summary="More efficient code">
~~~~~
#include <bits/stdc++.h>
using namespace std;
int main() {
int p, x, y;
cin >> p >> x >> y;
for (int s = y; ; s++) {
if (s % 50 != x % 50) {
continue;
}
bool me = false;
int i = s / 50 % 475;
for (int j = 0; j < 25; j++) {
i = (i * 96 + 42) % 475;
if (i + 26 == p) {
me = true;
...
]: print("unrated") exit()
Tutorial of VK Cup 2017 - Round 3
19.
New: Educational Rounds on Codeforces! Hi everybody!
First, I invite you to take part in an official [contest:597]. The fact is, the Codeforces team has made numerous changes to the platform (details are below), and we want to be sure that the basic functionality remained unchanged. This round will have a shortened duration of 1.5 hours, consist of 3 (maybe 4) problems that you might have already seen before. Its purpose is to test the system on the one hand, and on the other hand — to brighten up a Wednesday evening. Of course, the round will be unrated.
Now the main thing. This coming Friday (yes, the 13th of November) Codeforces starts another line of rounds. We called them Educational Rounds. Using my students at the Saratov State University Programmings Competitions Training Center as an example, I regularly notice that even those who have a considerable progress in the results on the rounds often have narrow purview in terms of standard topics and ideas, they are not familiar with many well-known problems ...
formal text of the statements; * Unrated (perhaps for now); * We will try to
conduct them in the, will be unrated.
20.
Copied problem in Codeforces Round #819 (Div. 1 + Div. 2) and Grimoire of Code Annual Contest 2022 While solving random problems on DMOJ I found this problem: [Problem](https://dmoj.ca/problem/tle16c8p6), [Contest the problem appeared in](https://dmoj.ca/contest/tle16c8). I only read the statement and decided it was not for me, so I moved on. Today after the round I remembered this problem because it seemed similar to [problem:1726F]. Not only are the problems exactly the same, they even share the same sample and the explanation of the sample is also the same:
Together with the fact that [user:little_angel,2022-09-06] has solved this problem on DMOJ:
I am convinced that the authors of [contest:1726] have purposefully copied the problem and didn't even try to hide it. I don't think the contest should be unrated, because the impact was not that big. But ...
even try to hide it. I don't think the contest should be unrated, because the
impact was not that big, try to hide it. I don't think the contest should be unrated, because the
impact was not that big. But
21.
Codeforces Round #743 Is Unrated: Investigating the Reason Hello.
Sorry for it. Actually, right now I don't have any idea why testing is so slow now. Obviously, it doesn't work as expected. It is not because of problems. So please don't blame writers or coordinators. I'm investigating the reason, but don't see it now.
I myself am very upset and I apologize to the authors, coordinator, and participants. I will do my best to find the cause and fix it. Surprisingly, we haven't made any big changes to this part of the system lately. But something went wrong.
Mike.
**UPD:** https://codeforces.com/blog/entry/95081#comment-841873
Codeforces Round #743 Is Unrated: Investigating the Reason
22.
TL Issue in the #659 (Div. 1) Problem F I've hacked all AC solutions of [this](https://codeforces.com/contest/1383/problem/F) problem, which were submitted during the contest, and I believe I can hack most of upsolving solutions.
Currently, I only checked that they time out on my local machine, because "Unexpected Verdict" prevents me from uphacking.
I even hacked model implementation in the editorial.
[Here](https://ideone.com/cHvjkp)'s my latest generator. Feel free to challenge it.
Side Note: [user:yosupo,2020-07-26] wrote a [solution](https://codeforces.com/contest/1383/submission/88036534), which passes the above case, but I failed it with another [generator](https://ideone.com/LKx3FP).
What I want to argue is that TL of this problem is too tight, and it affected some of the competitors.
For example, I got almost the same idea as the model solution during the contest. Still, I was too scared to write it because I suspected it would time out without full optimization and possibly some tweaks like shuffling ve...
the test) passed F, which seems unfair to me. I'm not saying the round should
beunrated; I think, I'm not saying the round should be unrated; I think there exists a really
well-optimized solution
23.
April Fools Day Contest 2023 Hello, Codeforces!
I, along with [user:AlperenT,2023-03-30], [user:Ari,2023-03-30], [user:BucketPotato,2023-03-30], [user:ScarletS,2023-03-30], and [user:ToxicPie9,2023-03-30], would like to invite everyone on Codeforces to the [contest:1812]! The 11th April Fools Day Contest will take place on [contest_time:1812]. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
Please note that the round is **unrated**.
In this round you'll be given $n$ weird problems and 2 hours to solve them, where $7 \leq n \leq 12$. At most $\sqrt{n}$ of the problems will be [interactive](https://codeforces.com/blog/entry/45307). The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them).
You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the ...
figuring out what the actual task is. Please note that the round is **unrated
**. In this round, Please note that the round is **unrated**.
Announcement of April Fools Day Contest 2023
24.
About Problem Coincidences Hi.
Of course, there was an unpleasant incident with the problem today. In fact, the problem almost coincided with another problem in the old round, which was hosted 5 years ago.
You, of course, are shocked. You, of course, think that the round should be unrated.
You are wrong. Here's why.
[cut]
We need to clearly distinguish between two scenarios with coincided problems in our rounds.
First. The writer has knowingly plagiarized. This is an outrageous scenario. Such behavior knows no excuse and it is a conscious detriment to our community. Shame on the writer!
Second. The problem was matched unintentionally. The writer was unaware of some old problem. This happens. The coordinator had not seen this old problem before or had forgotten it. We are all human. The round was tested, but the testers did not indicate such a coincidence. Too bad, it happens. Who can we blame for this situation? The writer? Most likely, the writer did a lot of work to prepare the ro...
course, are shocked. You, of course, think that the round should be unrated.
You are wrong. Here's, I am strongly against the creation of such a precedent. You can't make a round
unrated if, You, of course, are shocked. You, of course, think that the round should be
unrated.
25.
Codeforces: Results of 2020 [list some changes and improvements] Hello, Codeforces!
I understand that 2021 has been going on for a long time, but here I have picked up a subset of some of the improvements that the Codeforces team made in 2020. Soon I will publish numbers (no, charts) with statistics for 2020. In the meantime, I bring to your attention a list of changes and improvements.
By the way, this is a decent list. This is about half to a quarter of all changes. It's just that other changes are more often somewhere in the internals of the system and are not visible to users. Please read this list. Each item is the effort of someone from the team. Thanks to [user:geranazavr555,2021-03-14], [user:kuviman,2021-03-14] and [user:cannor147,2021-03-14] for their efforts. You've made our platform better! Well, by the way, I don't quit programming and many improvements were made by me.
The items on the list are written in a concise and informal form, many of the items I just copied from commit messages from git. If you want more details &mdash...
delete a mashup/contest * Ratings for new accounts are now calculated
differently *Unrated or, /contest * Ratings for new accounts are now calculated differently * Unrated or
non-positive rating
26.
Round #819 Unrated due to Problem Theft Hello Codeforces.
Unfortunately a few hours after the end of Round #819 we were pointed out that one of the problems was stolen from another online judge.
Codeforces team strongly condemns such an action from the author. By no means is this acceptable behavior. This is the first and the most important rule of problem making: your problem should be new up to your best knowledge.
A lot of people put lots of effort into creation of every single round. You can find these people mentioned in the announcements and they indeed deserve these acknowledgments. And yet a single cowardly decision can ruin this huge work and experience of thousands of participants.
In this particular case the copied problem was not widely known, and it seems that this made little or no impact on the course of the round. Nevertheless, we stick to the decision that in such case the round cannot be considered successful, and thus no rating changes can be applied. We will also remove the problem from the ro...
Round #819 Unrated due to Problem Theft
27.
Codeforces Round #632 (Div. 2) Hello, Codeforces!
I'm glad to invite you to my first round [contest:1333], which will take place on [contest_time:1333].
"Thank you" time!
I'd like to thank:
- [user:antontrygubO_o,2020-04-05] for coordination of the round.
- [user:300iq,2020-04-05], [user:nvmdava,2020-04-05], [user:aryanc403,2020-04-05], [user:antoshkin,2020-04-05], [user:lkosten,2020-04-05], [user:pavel-afonkin,2020-04-05] for testing and useful advices.
- [user:MikeMirzayanov,2020-04-05] for great systems Codeforces and Polygon.
- [user:CuriOusQuOkka,2020-04-05] for listening to my mumble while I came up with tasks.
- [user:antontrygubO_o,2020-04-05] for coordination of the round (again).
You'll be given 6 problems and 2 hours to solve them.
Point distribution will be announced as soon as possible.
Hope you will enjoy the round! Good luck and have fun!
**P.S: YES, IT'S RATED.**
**UPD**: Score distribution:
500 — 750 — 1250 — 1750 — 2000 — 2500.
**U...
Wow, there is no unrated in div2 round!, ] - [user:sweetwrapper,2020-04-08] - [user:wjli,2020-04-08] Wow, there is no
unrated in div2
Announcement of Codeforces Round 632 (Div. 2)
28.
COMPFEST 13 Finals Mirror (Unrated, ICPC Rules, Teams Preferred) <img alt="logo" src="/predownloaded/31/e8/31e886f0ba055023282a2f68b4b254d98c02c727.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Hi <strong><span style="color:#bfac00;">Code</span><span style="color:#006fbf;">for</span><span style="color:#b00000;">ces</span></strong> ଘ(੭*ˊᵕˋ)੭* ੈ♡‧₊˚!
We're delighted to invite you to [COMPFEST 13 — Finals Online Mirror (Unrated, ICPC Rules, Teams Preferred)](https://codeforces.com/contests/1575) on <a class="contest-time" contestid=1575></a>.
All problems were written and prepared by [user:hocky,2021-09-18], [user:steven.novaryo,2021-09-18], [user:rama_pang,2021-09-18], [user:JulianFernando,2021-09-18], [user:Zap,2021-09-18], [user:Panji,2021-09-24], [user:richiesenlia,2021-09-24], [user:Sakamoto,2021-09-24], and [user:Markus_geger,2021-09-24].
I would also like to thank:
- [user:KAN,2021-09-18] for helping to host the mirror round;
- ([user:AVM.Martin,2021-09-30], [user:Ace_02,202...
COMPFEST 13 Finals Mirror (Unrated, ICPC Rules, Teams Preferred), ; Finals Online Mirror (Unrated, ICPC Rules, Teams
Preferred)](https://codeforces.com/contests/1575) on, We're delighted to invite you to [COMPFEST 13 — Finals Online Mirror (Unrated,
ICPC Rules
29.
Invitation to CodeChef December Lunchtime 2020 We invite you to participate in CodeChef’s [December Lunchtime](http://bit.ly/LTIME91-Codeforces), this **Saturday, 26th December**, from [9:30 pm to 12:30 am IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=December+2020+Lunchtime&iso=20201226T2130&p1=44&ah=3).
**Note the unusual time.** It starts at 9:30pm instead of the usual 7:30pm
You will be given a total of **8 problems** (6 in Div2, 6 in Div1) to solve in a duration of **3 hours**.
Joining us on the problem setting panel are:
- Setters: Sahil [user:sahi1422,2020-12-25] Chimnani, Venkata [user:Nikhil_Medam,2020-12-25] Nikhil Medam, Áron [user:mraron,2020-12-25] Noszály, Nishant [user:nishant403,2020-12-25] Shah, Yogesh [user:SeismicToss,2020-12-25] Sharma, Hriday [user:the_hyp0cr1t3,2020-12-25], Divyam [user:divyamsingal01,2020-12-25] Singal, Bhavyesh [user:bhvdsi,2020-12-25] Desai
- Tester: Rahul [user:amnesiac_dusk,2020-12-25] Dugar
- Editorialist: Taranpreet [user:taran_1407,2020-12-25] Singh
...
**The contest is unrated due to queue and server issues.**
30.
Codeforces Round #723 (Rated for Div 2) Hello again Codeforces!
[user:Errorgorn,2021-05-25], [user:Oolimry,2021-05-25] and [user:ILoveIOI,2021-05-25] are glad to invite you to participate in [contest:1526] which will be held at [contest_time:1526]. The round will be **rated for the participants with a rating lower than 2100**. Participants from the first division are also welcomed to take part in the competition but it will be unrated for them.
You will be given **2 hours and 30 minutes** to solve **6 questions**. One of the puzzles is interactive, please read [the guide of interactive](https://codeforces.com/blog/entry/45307) [problems](https://en.wikipedia.org/wiki/Binary_search_algorithm) before the contest.
We would like to thank:
- Our lord and saviour [user:AntontrygubO_o,2021-05-25] for amazing coordination and rejecting our poopoo tasks
- [user:dantoh000,2021-05-25] and [user:tqbfjotld,2021-05-25] for roasting our enigmas and testing them before they were prepared
- our many testers [user:balbit,2021-05...
division are also welcomed to take part in the competition but it will be
unrated for them., unrated for them. You will be given **2 hours and 30 minutes** to solve **6
questions**. One of the
Announcement of Codeforces Round 723 (Div. 2)
31.
Codeforces Round #726 (Div. 2) #### Hello Codeforces!
[user:ssense,2021-06-15] and I are very glad to invite you to [contest:1537] which will take place on [contest_time:1537]. The round will be **rated for participants with a rating lower than 2100**. Division 1 participants are also welcomed to take part in the competition but it will be unrated for them.
The round was originally planned to be a division 3 round so the problems might be slightly easier than average Div 2.
You will be given **6 problems** and **2 hours** to solve them.
We would like to thank the following people:
- <a class="rated-user user-red" href="/profile/1-gon" title="yo-yo master">1-gon</a> for amazing coordination of our round!
- <a class="rated-user user-red" href="/profile/antontrygubO_o" title="orz Tester">antontrygubO_o</a> for testing, translating statements and providing useful ideas!
- <a class="rated-user user-legendary" href="/profile/Maksim1744" title="orz Tester">Maksim1744</a>, <a class="rated-user user-re...
but it will be unrated for them. The round was originally planned to be a
division 3 round so, **. Division 1 participants are also welcomed to take part in the competition
but it will beunrated for
Announcement of Codeforces Round 726 (Div. 2)
32.
About Rating Changes in AtCoder. TL;DR
What if we introduce the followings:
- You'll have a register-as-unrated button. You can switch rated and unrated only before opening a problem.
- If you are registered as a rated participant, you'll get rated when you open a problem, even if you don't submit.
Hello, community.
Currently, your AtCoder rating changes only if you submit to the contest.
This is also the case with Codeforces, so I think it's a standard.
However, this scheme clearly has a flaw; you can leave the contest without submission to keep your rating.
This implies you may get underrated because of those who didn't submit.
You would say things like this can happen only if you are a newcomer, and the effect will be negligible in the long term.
I generally agree with it, but sometimes even reds are affected by this issue.
I know some people intentionally submit CE code to make them rated.
At the same time, I know some people do the "Head to F" strategy or similar things and sometimes don't m...
fully participate in a contest or just want to watch it, you can register as
unrated participants and, - You'll have a register-as-unrated button. You can switch rated and unrated
only before opening a, TL;DR What if we introduce the followings: - You'll have a register-as-unrated
button. You
33.
AIM Tech Poorly Prepared Contest (unrated, funny, div. 1 preferred) Hello!
Traditionally AIM Tech organizes a big party for Petrozavodsk camp participants to have fun and get an opportunity to communicate with each other. Usually it comes along with **a funny contest in unusual format**. This year we decided to share the fun with all codeforces community!
This year we came up with a format requiring (probably) less time for preparing the contest. It is somewhat similar to an ordinary contest with a 3-hour duration. We already have some problem ideas, so it should be super easy to prepare the problems just one night before the competition. We hope everything will run smoothly!
The contest will start on [contest_time:1302]. It could be a bit rescheduled due to onsite delays.
It will be **an unrated funny competition**. Unlike usual ICPC-style contests, you'll be given an archive with several open test cases and answers for each problem. You'll have some sample test cases in the statement too, they'll be included in the archive. However, the ...
AIM Tech Poorly Prepared Contest (unrated, funny, div. 1 preferred), rescheduled due to onsite delays. It will be **an unrated funny competition**.
Unlike usual ICPC-style, It will be **an unrated funny competition**. Unlike usual ICPC-style contests,
you'll be given an
34.
COMPFEST 15 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred) <img alt="logo" src="/predownloaded/54/ec/54ec8a2a974eb225636db378f5470e039144d49b.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Hello, **Codeforces**! 😍😍
We are happy to invite you to participate in [COMPFEST 15 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred)](https://codeforces.com/contests/1866) on <a class="contest-time" contestid=1866></a>. COMPFEST is a national **ICPC-style contest** for university students in Indonesia.
The problems are written and prepared by [user:ArvinCiu,2023-08-30], [user:asteriskzie,2023-08-30], [user:CyberSleeper,2023-08-30], [user:Edbert.H,2023-08-30], [user:FreeJinG,2023-08-30], [user:gansixeneh,2023-08-30], [user:KokiCoder,2023-08-30], [user:nandonathaniel,2023-08-30], and [user:Pyqe,2023-08-30].
We would also like to thank:
- [user:KAN,2023-08-30] for helping to host the mirror round;
- [user:AMnu,2023-08-30], ([user:KerakTelor,2023-08-30], [user:Owmic...
COMPFEST 15 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred), Online Mirror (Unrated, ICPC Rules, Teams
Preferred)](https://codeforces.com/contests/1866) on, We are happy to invite you to participate in [COMPFEST 15 Preliminary Online
Mirror (Unrated, ICPC
35.
About the Codeforces Round #637 Hello Codeforces.
I'm writing this post to make comments about a situation on the last Codeforces Round and tell the bad news. We did many mistakes and due to them, the round caused much dissatisfaction from the Codeforces community.
Some of our mistakes:
1. Some stupid mistakes in the statements.
2. In the problem D2E/D1C the numbers $d_i$ were not necessarily sorted, but there were no pretests for that.
3. The checker of the problem D2F/D1D didn't check one of the requirements and due to that $8$ solutions failed on pretests during the system testing.
4. After the editorial was posted the mistake was found in the main solution of the problem D1E ([more details here](https://codeforces.com/blog/entry/76479?#comment-609911)). Now we don't know the correct solution.
So, the round was very unsuccessful, I'm very sorry about this. I will make conclusions and will try to avoid such situations later. Please, treat with respect to the authors, even in such a bad situatio...
round unrated, Div2 round is still rated**, Sorry for all, who had a big
positive rating change., wrong checker and the wrong solution, we decided to make **Div1 round unrated,
Div2 round is still
36.
Stop unrated users from sending talk messages! Today I received this incredibly offensive talk message from an unrated account (also with an offensive username), which attacks me based on my national origin:
I strongly suspect that I am not the only Codeforces user receiving such messages recently (I don't think I am particularly notable in any aspect as a Codeforces user, and I cannot think of a reason why I might be specifically targeted); if you received similar messages, let me know in the comments.
I am aware of the "block user" feature and the ability to require a minimum rating for users to send messages to you, but it is not very well-known and is simply insufficient.
**Update: after receiving the message, I set a "at least newbie" setting for users to send talk messages to me. However, two unrated users still managed to message me after the blog post was created. This seems to be a Codeforces bug.**
I therefore request that unrated users...
Stop unrated users from sending talk messages!, messages to me. However, two unrated users still managed to message me after
the blog post was created, I therefore request that unrated users be prohibited from sending talk
messages. We should also, Today I received this incredibly offensive talk message from an unrated account
(also with an
37.
Codeforces Round 918 (Div. 4) Happy Holidays Codeforces! 🎅
[user:mesanu,2023-12-27], [user:flamestorm,2024-04-22] and I are very excited to invite you to [contest:1915]! It starts on [contest_time:1915].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants of the f...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated, ratings less than 1400 or you are an unrated participant/newcomer). We urge
participants whose rating
Announcement of Codeforces Round 918 (Div. 4)
38.
Valentine's Day Contest 2020 Hello everyone!
Will you be single and bored during Valentine's Day? Never fear, as [user:zscoder,2020-02-06] is here to cure your boredom.
I would like to invite you to Valentine's Day Contest 2020, which will take place on [Friday, February 14, 2020 at 12:30 GMT](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20200214T2030&p1=122&ah=3&am=30). The contest is unofficial and unrated, but the quality of most (if not all) of the problems are comparable to problems from a Codeforces round. I am the author of all problems.
The contest format will be IOI format, which means that each problem is worth $100$ points, and there are subtasks for each problem. There will be no time penalty. The problems are **not sorted in increasing order of difficulty**. Unlike IOI, you are allowed to use any templates or notes you have.
There are **7 problems** to be solved in **3.5 hours**. There is an interactive problem, so feel free to learn about them [here](https://codeforces.com/...
&p1=122&ah=3&am=30). The contest is unofficial and unrated, but the quality of
most (if not all) of, unrated, but the quality of most (if not all) of the problems are comparable to
problems from a
Announcement of Valentines Day Contest 2020
39.
April Fools Day Contest 2020 The contest is over; I hope you enjoyed it! The editorial is available [here](https://codeforces.com/blog/entry/75480).
---
The 8th April Fools Day Contest will take place on Wednesday [April 1st](https://www.timeanddate.com/worldclock/fixedtime.html?day=1&month=4&year=2020&hour=17&min=35&sec=0&p1=166). This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
In this round you'll be given several weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the contests of the past years: [2012](http://codeforces.com/contest/171), [2013](http://codeforces.com/contest/290), [2014](http://codeforces.com/contest/409)...
solved problems and penalty time earned on them), and it will be unrated. You
can submit solutions, time earned on them), and it will be unrated. You can submit solutions in any
language allowed by
Announcement of April Fools Day Contest 2020
40.
Educational Codeforces Round 163 [Rated for Div. 2] <img alt="Neapolis University Pafos" src="/predownloaded/9a/33/9a332fadbb47050ba9405057df022a6e37eaf5c0.png" style="float:right;height: 200px; margin: 10px; max-width:40%;"/>
Hello Codeforces!
We are pleased to announce a new long-term partnership between Codeforces and [Neapolis University Pafos](https://www.nup.ac.cy/). Now educational rounds will be supported by Neapolis University Pafos. Stay tuned and you will find out more soon.
On [contest_time:1948] [contest:1948] will start.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user...
on problem E changed may request unrated participation (they have received the
directions on how to, participants whose verdict on problem E changed may request unrated
participation (they have received the
Announcement of Educational Codeforces Round 163 (Rated for Div. 2)
41.
[Contest] Statement Not Found: Season 2 #### Do you think you can solve CP problems without reading the problem statements? Let's find out!
On [August 28, 2022 (Sunday) 19:30-22:00 GMT+8](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Statement+Not+Found+-+Season+2&iso=20220828T1930&p1=122&ah=2&am=30), I will hold an unofficial fun contest called Statement Not Found. As you can deduce from the title, there will be no problem statements (except title and samples). Your goal is to collect as many points as possible within 2.5 hours :)
Obviously, this round is **unrated**. It is somewhere between April Fools contest and a legitimate contest.
The contest will be OI-style, meaning there will be no time penalty. You are allowed to use any resources online to help solve the problems. There will be **12** problems.
**Scoring Distribution:** 200-400-700-700-700-800-800-900-1100-1100-1100-1500 (Total: 10000)
**Please read all problems** as problem difficulty is very subjective and a 1100-point problem might b...
Obviously, this round is **unrated**. It is somewhere between April Fools
contest and a legitimate
42.
Codeforces Round #838 (Div. 2) Hello, Codeforces!
[user:amurto,2022-12-13] and I are glad to invite everyone to participate in [contest:1762], which will be held on [contest_time:1762].
This Round will be rated for participants with rating strictly **lower than 2100**. Participants from the first division are also welcomed to take part in the competition but it will be unrated for them.
You will be given **7 problems** and **2 hours and 30 minutes** to solve them. One of the problems will be **interactive**. Make sure to read [this blog](https://codeforces.com/blog/entry/45307) and familiarize yourself with these types of problems before the round!
We would like to thank:
- [user:errorgorn,2022-12-13] for amazing coordination and help with the problem preparation.
- [user:KAN,2022-12-13] for translation of the statements into Russian
- [user:TheScrasse,2022-12-13] for providing suggestions which helped us to improve one problem.
- [user:GoatTamer,2022-12-13] for discussing problems with us whil...
from the first division are also welcomed to take part in the competition but
it will beunrated for
Announcement of Codeforces Round 838 (Div. 2)
43.
InterviewForces Contest #1 (Div. 7) Hi Codeforces!
We are pleased to invite you to [contest:383377], which will take place on [contest_time:383377]. You will be given 9 problems and 2 hours to solve them. **Please follow [this link](https://codeforces.com/contestInvitation/b5b8b43069d2d6ea2be442e374a71a84985bae68) in order to register for the contest.** Note that this contest is not an official Codeforces round.
The round will be unrated for all participants. It will be held according to modified ICPC rules.
All problems in this round were written and prepared by [user:dorijanlendvaj,2022-05-22], [user:errorgorn,2022-05-22], [user:juckter,2022-05-22], [user:nor,2022-05-22] and [user:ToxicPie9,2022-05-22]. We have worked on this round for quite a short time and hope you find every problem <s>so easy that even your five year old sibling could solve it</s> interesting.
This round is sponsored by [user:errorgorn,2022-05-22] and [user:Sexpert,2022-05-24] with the following prizes:
- 1st place: 10 lakh VEF
- 2n...
The round will be unrated for all participants. It will be held according to
modified ICPC rules.
44.
Codeforces Team To Do List ***This blog is to list common bugs/suggestions/complaints for [user:MikeMirzayanov,2022-09-09]. Share your ideas in the comments so I can add them to the list.***
- Make offical dark mode.
- Add discussion section for each problem in the editoral.
- Add unrated registeration.
- Make upvotes and downvotes changable.
- Rename "friends" to "followers".
- Add report user option.
- Add the dislike button([dislikes:1]).
- Change hacked code verdict to "Verdict"(hacked) instead of just "Hacked".
- Problem submission syncing *(i.e. if you solve a problem in a mashup or a div 2, your submission will show up in the div 1 version of the problem as well)*.
- Seperate show tags and show problem rating options for problemset.
- An option for excluding tags when filtering problems *(for example, let's say I want to do some DP problems, but I don't want greedy proble...
45.
Codeforces Round #536 (Div. 2) Hello, Codeforces!
It's my honor to invite you to Codeforces Round #536 (Div. 2), which takes place at [12:35 UTC, January 31st, 2019](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Codeforces+Round+%23536+%28Div.+2%29&iso=20190131T1235&p1=1440&ah=2). The round will be **rated** for all division 2 participants **(with rating less than 2100)**. Also we warmly welcome those division 1 participants to join us out of competition.
This is my second round on Codeforces platform, and my first round was on January 31st, **2018**, which is such a coincidence that I would like to say thanks to [user:KAN,2019-01-29] for his awesome coordination and great dedication to this round. Besides, much thanks to testers [user:Aleks5d,2019-01-29], [user:cyand1317,2019-01-29], [user:mohammedehab2002,2019-01-29], [user:osaaateiasavtnl.,2019-01-29] for their excellent testing work. Also, I would like to appreciate the Codeforces platform created and maintained by [user:MikeMirzayanov,2019-01-...
participation and dedication even after the unrated announcement. :) **UPD4:**
The **real** [Editorial, us with. Thanks for your participation and dedication even after the unrated
announcement. :), **UPD5:** Despite that the round is **unrated**, I have to announce the
winners, who deserve it
Announcement of Codeforces Round 536 (Div. 2)
46.
COMPFEST 14 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred) <img alt="logo" src="/predownloaded/03/5f/035ff83d655937b478f5fe9f351f79ac0781f6d2.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Hello, **Codeforces**! 🤗
We are happy to invite you to participate in [COMPFEST 14 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred)](https://codeforces.com/contests/1725) on <a class="contest-time" contestid=1725></a>. COMPFEST is a national **ICPC-style contest** for university students in Indonesia.
The problems are written and prepared by [user:Pyqe,2022-09-02], [user:steven.novaryo,2022-09-02], [user:Nyse,2022-09-02], [user:muhammadhasan01,2022-09-02], [user:gansus,2022-09-02], [user:nandonathaniel,2022-09-02], [user:FerdiHS,2022-09-02], [user:TakeMe,2022-09-02], and [user:NeoZap,2022-09-02].
We would also like to thank:
- [user:KAN,2022-09-02] for helping to host the mirror round;
- rama_pang ([user:rama_pang,2022-09-02], [user:zappeko,2022-09-02], [user:Berted,202...
COMPFEST 14 Preliminary Online Mirror (Unrated, ICPC Rules, Teams Preferred), Mirror (Unrated, ICPC Rules, Teams
Preferred)](https://codeforces.com/contests/1725) on, We are happy to invite you to participate in [COMPFEST 14 Preliminary Online
Mirror (Unrated, ICPC
47.
SWERC 2021-2022 <img src="/predownloaded/4a/fc/4afcde700751b1ef849737c2edd64e52901e8df3.png" style="width:250px; float:right; margin: 0 1em 1em 1em"/>
The Southwestern Europe Regional Contest will take place on the 23rd of April.
It is the ICPC regional contest (i.e., the winning teams will advance to the ICPC World Finals) for teams from France, Israel, Italy, Portugal, Spain, and Switzerland.
The mirror contest [contest:1662] will be held on Codeforces at [contest_time:1662] and will last 5 hours.
The mirror contest will contain all the problems from the official competition plus some additional problems.
I am the chief judge for the competition and I want to thank:
- The amazing set of judges who proposed and prepared the problems: [user:cescmentation_folch,2022-04-04], [user:cip999,2022-04-04], [user:Delfad0r,2022-04-04], [user:gangsterveggies,2022-04-04], [user:giove,2022-04-04], [user:gog.gerard,2022-04-04], [user:majk,2022-04-04],
[user:Petr,2022-04-04], [user:Simon,2022-04-04...
1. The contest is unrated, so your codeforces rating will not be affected. 2.
The scoring is ICPC
48.
About Codeforces Round #682 (Div. 2) Hello.
As you already know the round was declared unrated. Firstly, we're extremely sorry that this happened and hope you enjoyed solving the problems regardless.
About what happened, the constraints for B were $t = 100$ and $n = 1000$ from the beginning i.e. for more than a month.
This problem was supposed to be A initially, so I kept lower constraints than usual to ensure a small queue. At the same time, I didn't want trivial brutes to pass, so $n = 1000$ seemed like a good choice. Around 1 hour before the contest, a tester reminded me of his earlier feedback about increasing the number of test cases and adding a constraint on the sum of $n$, which would also make it more clear whether $\mathcal{O}(n^2)$ solutions should pass or not. At the same instant, I gave him WRITE access on polygon so that he could review all the problems.
Unfortunately, there was some miscommunication on my part leading him to think I have asked him to update the constraints. As a result, he upd...
As you already know the round was declared unrated. Firstly, we're extremely
sorry that this
49.
Situation with Round 421 problem div. 1A/div. 2C During the discussion after the Round 421 it turned out that the author's solution was wrong. Yes, we had several testers, we had a bruteforce solution that worked correctly, we had a stress testing between the bruteforce and the main solutions. However, all these measures haven't prevented the mistake: the testers haven't noted the issue, the stress haven't found any counter-tests. The solutions also produced the same answers all small tests we had in the testset, so we only found the issue when a test used for a hack was added.
We are terribly sorry about the mistake. We did our best to ensure the problems are ok, I don't know any available method that we haven't used to check the problem.
We've spent the last few hours trying to come up with a new, correct solution to the problem, but right now I don't see any solution that seems undoubtedly correct to me. There are a few that work better than the author's, but yet unproved, you can try to prove [this one](http://codeforces.co...
Thus, I apologize that the round should be declared unrated. Hope for your
understanding., unrated. Hope for your understanding.
50.
A purple's message to Mike (About Problem Coincidences) Dear [user:MikeMirzayanov,2023-02-12],
Although you want the round to be rated, I, [user:pwned,2023-02-12], believe the contest should remain unrated.
Making the round rated would be unfair. For instance, participants who blatantly copied the code for F would have a massive advantage. Problem F was worth a staggering 3250 points at the beginning of the round, outweighing the entirety of ABC! Meanwhile, participants who got the first four problems would have their positive delta stolen. At the extreme end, the users who focused on problem F, thinking it is simple, will have an even more pronounced disadvantage. Consider those who skipped D to look at F. These users hastily scribbled on their scratch papers, trying to find a swift solution. They would soon discover that they were attempting a 3100-rated monstrosity!
Codeforces should not use an author's intentions to decide whether a round must be rated. Instead, we must view the situation from a participant's perspective. An un...
remain unrated., Therefore, my humble opinion on the best course of action is to make this round
unrated and have
51.
Codeforces Round #784 (Div. 4) Hello Codeforces!
[user:SlavicG,2022-04-19], [user:flamestorm,2022-04-19], [user:MikeMirzayanov,2022-04-19], [user:Errichto,2022-04-19], and I want to invite you to the long-awaited second Div. 4 round!
It starts on [contest_time:1669].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the off...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated, the rating will be recalculated for all with initial ratings less than 1400 or
you are anunrated
Announcement of Codeforces Round 784 (Div. 4)
52.
Codeforces Round #373 Hi everyone!
Codeforces Round #373 (Div. 1 + Div. 2) will take place on [23 September 2016 at 16:05 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?day=23&month=9&year=2016&hour=16&min=5&sec=0&p1=166). Please note that **the timing is unusual**.
This time tasks for you were prepared by me (Matvey Aslandukov) and my brother [user:_XuMuk_,2016-09-21] (Andrew Aslandukov). It is our first codeforces round and we hope you'll enjoy it. We want to say special thanks to [user:Seyaua,2016-09-21] (Ievgen Soboliev), [user:alexfetisov,2016-09-21] (Alexandr Fetisov) and [user:winger,2016-09-21] (Vladislav Isenbaev) for testing the problems, [user:GlebsHP,2016-09-21] for his help with the contest preparation, and [user:MikeMirzayanov,2016-09-21] for the excellent platforms Polygon and Codeforces.
Coincidentally, the date of the round falls on my birthday, so I am very happy that I can spend that day surrounded by our friendly community :)
There will be five problems and two hou...
each particular participant. As a result, **the contest for division one will
beunrated**., solution and answers on pretests will be the same, the round may be rated.
Otherwise, it will beunrated., will be the same, the round may be rated. Otherwise, it will be unrated. Thus
final results
Announcement of Codeforces Round 373 (Div. 1)
Announcement of Codeforces Round 373 (Div. 2)
53.
Codeforces Round #601 Hello Codeforces!
I am glad to invite you to [Codeforces Round #601](https://codeforces.com/contests/1254,1255), which will take place on [contest_time:1254]. The round will be rated for both divisions.
All problems in this round were created and prepared by a team of all-Vietnamese setters: [user:MofK,2019-11-18], [user:Prof.PVH,2019-11-18], [user:UncleGrandpa925,2019-11-18], [user:ngk,2019-11-18]. This is the first Vietnamese Div1 round. We tried to make both the problems and the statements interesting and hope that you will enjoy them!
There is an interactive problem in the round. You can read the guide for interactive problem [here](https://codeforces.com/blog/entry/45307).
We would like to give a lot of thanks to:
- [user:MikeMirzayanov,2019-11-18] for the amazing platforms Codeforces and Polygon.
- [user:arsijo,2019-11-18] for excellent coordination and many valuable advice for the round.
- Our team of testers: [user:MikeMirzayanov,2019-11-18], [user:KAN,20...
[user:MikeMirzayanov,2019-11-19]. If the issue heavily affected you and you
want the round to beUNRATED for you, you want the round to be UNRATED for you, you can fill the appeal form by the
link: https
Announcement of Codeforces Round 601 (Div. 1)
Announcement of Codeforces Round 601 (Div. 2)
54.
Retiring from rated contests I've been thinking of retiring from algorithm contests for a while, having failed to qualify for any on-sites in 2017 or 2018 (I'm excluding DCJ from algorithm contests). This is definitely a young person's game and I can feel I'm not as sharp as I used to be. I still love problem solving, but when I'm under time pressure and just can't see the solution and know my rating is going to crash, I get so stressed and frustrated that I don't enjoy it any more.
Now that both my Topcoder and Codeforces ratings are back over 3000 I've decided to retire from rated contests so that I'll go out on a high. I will most likely continue to do unrated contests where if I have a bad day I can just walk away instead of stressing myself out. I might also get more involved in testing contests.
high. I will most likely continue to do unrated contests where if I have a bad
day I can just walk, rated contests so that I'll go out on a high. I will most likely continue to do
unrated contests where
55.
AtCoder's new rated/unrated registration format It seems AtCoder is going to implement a new system where you choose if your participation in a contest is rated or unrated before you get to see the problems. Here are the full details from the [site](https://atcoder.jp/posts/745):
> We developed a new system where one can choose Rated or Unrated participation in contests. We will introduce this system from ABC230 on 3rd Dec.
> When registering for a rated contest, you can decide whether you want to be Rated or Unrated in advance. You can choose an option before the contest starts or in the first five minutes of the contest. If you choose Rated, your rating will be updated whether or not you open problems or make submissions.
> In a rated contest, you can open problems only after you choose Rated or Unrated participation. If you don't choose an option and five minutes have passed after the contest starts, you are considered Unrated. Also, if your rating doesn't fall within the rated range of the contest, you are automatically...
AtCoder's new rated/unrated registration format, contest is rated or unrated before you get to see the problems. Here are the
full details from the, > Before a contest starts, you can switch Rated/Unrated by first canceling your
registration and, > In a rated contest, you can open problems only after you choose Rated or
Unrated participation, > Unrated: If you don't expect your typical performance for some reason but
still want to see the, > We developed a new system where one can choose Rated or Unrated participation
in contests. We, > When registering for a rated contest, you can decide whether you want to be
Rated orUnrated in
56.
Codeforces Round #708 Editorial We are really sorry to make the round unrated. Anyway, we hope that you enjoyed the problems!
[problem:1497A]
Idea: [user:shishin,2021-03-14]
<spoiler summary="Tutorial">
[tutorial:1497A]
</spoiler>
<spoiler summary="Implementation">
~~~~~
// один манул
#include <bits/stdc++.h>
using namespace std;
int main() {
int T;
cin >> T;
while (T --> 0) {
int n;
cin >> n;
vector<int> a(n);
for (int i = 0; i < n; ++i) cin >> a[i];
sort(a.begin(), a.end());
vector<int> b;
for (int i = 0; i < n; i++) {
if (i == 0 || a[i] != a[i - 1]) {
b.emplace_back(a[i]);
}
}
for (int i = 0; i < n; i++) {
if (i > 0 && a[i] == a[i - 1]) {
b.emplace_back(a[i]);
}
}
for (auto x : b) cout << x << ' ';
cout << '\n';
}
return 0;
cout << "amogus";
}
~~~~~
</spoiler>
[pr...
We are really sorry to make the round unrated. Anyway, we hope that you enjoyed
the problems!
Tutorial of Codeforces Round 708 (Div. 2)
57.
Please stop letting unrated accounts post and comment I think the fact that people can just make a new account anytime they want and start posting or commenting makes it very "easy" to spam. I've had that opinion since quite sometime but didn't say anything but today something happened which makes me think that this is of extreme importance.
**Commenting from a new unrated account is like saying stuff without consequences** : When you've given a few contests and spent some time on your account then you have an identity. Making a new fake account is equivalent to wearing a mask.
Take for example today's incident-
So there's this blog on codeforces "[Code For Athoy — Contest for Saving a Life](https://codeforces.com/blog/entry/78104)". It's basically a contest announcement as well as a person asking for donations for a cancer patient.
Now on that thread I see an absolutely insensitive jerk, just look at the audacity of this person. Here's [his comment](https://codeforces.com/blog/entry/78104?#comment-633189)
![ ](/predownload...
Please stop letting unrated accounts post and comment, **Commenting from a new unrated account is like saying stuff without
consequences** : When you've, While banning unrated people won't end spamming completely it'd definitely
reduce it, plus I don't
58.
Invitation to NUS CS3233 Final Team Contest 2023 Mirror <img alt="logo" src="/predownloaded/7a/2d/7a2da3823042e763e0d15d6571ba0bcb38139f90.png" style="float: right;height: 100.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
Hello, Codeforces community!
We are happy to invite you to participate in [National University of Singapore (NUS) CS3233 Final Team Contest 2023 Mirror](https://codeforces.com/contestInvitation/3d3b392eb92ff65022128f4e22462d5eaff55a25) on [Monday, April 10, 2023, at 09:35 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?day=10&month=4&year=2023&hour=12&min=35&sec=0&p1=166). CS3233 is a course offered by NUS to prepare students in competitive problem solving.
The contest is unofficial and will be held in Codeforces Gym. Standard ICPC rules **(Unrated, ICPC Rules, Teams Preferred)** apply. **The contest is unrated**. **Note the unusual starting time**.
The problems are written and prepared by [user:user202729_,2023-04-08], [user:rama_pang,2023-04-08], and [user:pooty,2023-04-08].
We wo...
held in Codeforces Gym. Standard ICPC rules **(Unrated, ICPC Rules, Teams
Preferred)** apply. **The, The contest is unofficial and will be held in Codeforces Gym. Standard ICPC
rules **(Unrated, ICPC
59.
Codeforces Practice Tracker — Browser Extension Hi everyone!
I'd like to share with you my new extension, [**Codeforces Practice Tracker**](https://chrome.google.com/webstore/detail/cnahgdhboflcnojgmeehhhfeoojifonm).
Codeforces Practice Tracker helps to track your practice progress in codeforces through time phases, It simply adds new tab to your profile (or any other profile) in this tab you can find data about each time phase.
For each time phase it shows:
- Number of solved problems.
- Number of submissions.
- Hardest (Max Rated) problem you solved.
- Average of the rates of the problems you solved.
- Number of contests and virtuals you participated.
- Statics of submissions.
Note: Gyms problems and unrated problems are only considered in number of solved problems and number of submissions.
More features:
- Show each phase and compare it with previous one.
- Skip inactive phases.
- Change number of days of each phase.
It ...
Note: Gyms problems and unrated problems are only considered in number of
solved problems and
60.
Virtual participation is great! I want to promote the option of virtual participation in contests, since I noticed it's not used as often as it could be. Perhaps it's just not something people keep in mind, but I'm sure that if you use it often, it will help you a lot.
What does it do? It allows you to compete in past contests as if you were actually competing when the contest took place — there are only two differences:
- it's unrated
- there are no hacks and so far, no pretests
Virtual participation is a great way to compete without worrying about your rating. Instead of making a fake account that you then throw away, you can just participate with your real account with no risk. If you care about embarassing yourself with poor performance, don't worry about it. Nobody cares.
Virtual participation is also a great way to train. Unlike regular upsolving, you have a timer, so you can't just take your time trying stupid shit or overthinking. This way, it's much better for training fast thinking. Takin...
- it's unrated - there are no hacks and so far, no pretests
61.
European Championship 2024 (EUC) <img src="/predownloaded/63/de/63dec3490d33610bedca123ae665430ca7387d6a.png" style="width:250px; float:right; margin: 0 1em 1em 1em"/>
The [European Championship 2024](https://euc.icpc.global/) will take place on the 24th of March in Prague.
The top teams from the European ICPC regionals CERC, NWERC, SEERC, SWERC will compete for the title of European champions. It is the first edition of this ICPC super-regional.
The mirror contest [contest:1949] will be held on Codeforces at [contest_time:1949] and will last 5 hours.
The mirror contest will contain the same problems as the official competition.
I am the chief judge for the competition and I want to thank:
- The amazing set of judges who proposed and prepared the problems: [user:antontrygubO_o,2024-03-19], [user:bicsi,2024-03-19], [user:giove,2024-03-19], Martin Kacer, [user:MZuenni,2024-03-19], [user:Petr,2024-03-19].
- Our beloved tester [user:ksun48,2024-03-19] who showed us that our perception of the difficultie...
1. The contest is unrated, so your codeforces rating will not be affected. 2.
The scoring is ICPC
62.
Live online mirror of The 2024 ICPC Asia Pacific Championship Hi,
We would like to invite you to participate in the [live online mirror contest of The 2024 ICPC Asia Pacific Championship](https://codeforces.com/contests/1938) next weekend.
ICPC Asia Pacific Championship is a new playoff round introduced to the Asia Pacific region this year. It is the contest for top non-winning teams from all regional contests in the region to qualify to the World Finals. See the [region rules](https://icpc.iisf.or.jp/asia-pacific/top/2023-24-cycle/) and [competition page](https://icpc.asia/) for more details.
The official contest is scheduled to start at [Saturday, 2 March 2024, 9am (UTC+7)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=The+2024+ICPC+Asia+Pacific+Championship&iso=20240302T09&p1=95&ah=5). The live online mirror contest is scheduled to start [**only 5 minutes later**](https://www.timeanddate.com/worldclock/fixedtime.html?msg=The+2024+ICPC+Asia+Pacific+Championship+-+Online+Mirror&iso=20240302T0905&p1=95&ah=5), to keep both conte...
The contest will use ICPC-style scoring (same as the official contest) and will
beunrated. You can
63.
Codeforces Round 445 (and Technocup 2018 — Elimination Round 3) Hi all!
This weekend, at [16:05 UTC on November 12th, 2017](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Codeforces+Round+%23445&iso=20171112T1905&p1=166&ah=2) we will hold Codeforces Round 445. It is based on problems of Technocup 2018 Elimination Round 3 that will be held at the same time.
Technocup is a major olympiad for Russian-speaking high-school students, so if you fall into this category, please register at <a href="https://technocup.mail.ru/">Technocup 2018 website</a> and take part in the Elimination Round.
I want to thank [user:MrKaStep,2017-11-12], [user:komendart,2017-11-12], [user:veschii_nevstrui,2017-11-12], [user:bixind,2017-11-12], [user:AndreySergunin,2017-11-12] and [user:DPR-pavlin,2017-11-12], who authored and prepared problems for Technocup, and [user:lewin,2017-11-12], who kindly suggested the last problem. I also want to thank [user:zemen,2017-11-12] and [user:AlexFetisov,2017-11-12] for testing the round.
Div. 1 and Div.2 editions are...
**UPD:** We apologize that we run into technical issues during the round. The
round will beunrated
Announcement of Технокубок 2018 - Отборочный Раунд 3
64.
Invitation to BNPCHS 2023 Elimination Round (Mirror, Unrated) <img src="https://media.discordapp.net/attachments/822512645395578902/1154984676222574592/header_ex_tmoc_2.png" alt="" style="width: 350.0px;max-width: 100.0%;max-height: 100.0%;">
We are excited to invite you to [BNPCHS 2023 Elimination Round (Mirror, Unrated)](https://tlx.toki.id/contests/bnpchs-2023-penyisihan-mirror) on [Saturday, September 23, 2023, 19:05 UTC+7](https://www.timeanddate.com/worldclock/fixedtime.html?msg=BNPCHS+2023+Elimination+Round+%28Mirror%2C+Unrated%29&iso=20230923T1905&p1=3909&ah=3).
The contest will be 3 hours long and will feature 6 problems. The contest difficulty will be similar to Codeforces Div. 3 Rounds. The order of the problems is different from the original BNPCHS contest.
The problems were written by [user:Owmicron,2023-09-21] [user:vioalbert,2023-09-21] [user:siplusplus,2023-09-21] [user:SunShine11,2023-09-21].
Problem components were prepared by [user:Owmicron,2023-09-21] [user:vioalbert,2023-09-21] [user:Chrisedyong,2023-09-21] [user:...
Invitation to BNPCHS 2023 Elimination Round (Mirror, Unrated), to invite you to [BNPCHS 2023 Elimination Round (Mirror, Unrated
)](https://tlx.toki.id/contests, We are excited to invite you to [BNPCHS 2023 Elimination Round (Mirror, Unrated
)](https
65.
VK Cup 2017 — Wild-card раунд 1 Hi all!
Tomorrow, on [April 5th 2017, at 15:35 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?msg=VK+Cup+Wild-card+Round+1&iso=20170405T1835&p1=166&ah=2) the first Wild-card Round of VK Cup 2017 will be held. Along with it there will be parallel unofficial round in which everyone can take part.
The rounds will use **special rules, the rounds will be unrated.** The problems were prepared by Codeforces team.
The detailed rules will be added to this post 30 minutes before the rounds. I can say now that there will be 24-hours open hacks phase after the round, like in Codeforces Educational Rounds.
**Round rules:**
The round will be almost usual contest with ACM ICPC rules. There will be 12 problems for 2 hours. During the round your solutions will be tested on some basic tests, they should be much stronger than usual pretests.
After the round you will have 24 hours to find tests against other participants’ solutions, this part is the same as in Educational round...
The rounds will use **special rules, the rounds will be unrated.** The problems
were prepared by
Announcement of VK Cup 2017 - Wild Card Round 1 (Unofficial Public Mirror)
Announcement of VK Cup 2017 - Wild Card Round 1
66.
Codeforces Round #724 (Rated for Div 2) Hello Codeforces!
We, the disciples of Omkar ([user:qlf9,2021-06-04], [user:tlatoani,2021-06-04], [user:hu_tao,2021-06-04], [user:golions,2021-06-04], and Omkar's newest disciple, [user:rabaiBomkarBittalBang,2021-06-04]), have written our third contest: [contest:1536] — [Omkar 3](https://www.youtube.com/watch?v=MI-pw4DdHEw). It will be held on [contest_time:1536] and will be rated for users in Division 2 (rating lower than 2100). As usual participants with rating >= 2100 are allowed to compete too, but the contest will be unrated for them.
You will be given **2 hours** to solve **6 problems**. There may or may not be an interactive problem, so it would behoove you to read the [guide for interactive problems](https://codeforces.com/blog/entry/45307). There also may or may not be competitive programming problems, so you should be sure to thoroughly understand everything [here](https://codeforces.com/blog/entry/91363).
We would like to thank:
- [user:antontrygubO_o,2021-...
contest will be unrated for them.
Announcement of Codeforces Round 724 (Div. 2)
67.
Codeforces Round #799 (Div. 4) Hello Codeforces!
[user:mesanu,2022-06-12], [user:flamestorm,2022-06-12], [user:MikeMirzayanov,2022-06-12] and I want to invite you to [contest:1692]! It starts on [contest_time:1692].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants of th...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated, ratings less than 1400 or you are an unrated participant/newcomer). We urge
participants whose
Announcement of Codeforces Round 799 (Div. 4)
68.
SWERC 2022-2023 <img src="/predownloaded/70/37/703737cf76db63e4b7bbb9fd63a01a3dc446371e.png" style="width:250px; float:right; margin: 0 1em 1em 1em"/>
The Southwestern Europe Regional Contest will take place on the 19th of February in Milan.
It is the ICPC regional contest (i.e., the winning teams will advance to the ICPC World Finals) for teams from France, Israel, Italy, Portugal, Spain, and Switzerland.
The mirror contest [contest:1776] will be held on Codeforces at [contest_time:1776] and will last 5 hours.
The mirror contest will contain the problems from the official competition plus some additional problems.
I am the chief judge for the competition and I want to thank:
- The amazing set of judges who proposed and prepared the problems: [user:cescmentation_folch,2023-01-24], [user:cip999,2023-01-24] (vice chief judge), [user:gangsterveggies,2023-01-24], [user:giove,2023-01-24], [user:gog.gerard,2023-01-24], [user:jinlifu1999,2023-01-24],
[user:Petr,2023-01-24], [user:Simon,2023...
1. The contest is unrated, so your codeforces rating will not be affected. 2.
The scoring is ICPC
69.
XVIII Open Olympiad in Informatics (Unrated, Online Mirror, IOI rules) Hi everybody,
In a few days there will be a Moscow Open Olympiad. This olympiad is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Olympiad in Programming, Moscow Team Olympiad, and Megapolis Olympiad (rounds <a href="https://codeforces.com/blog/entry/21185">327</a>, <a href="https://codeforces.com/blog/entry/23309">342</a>, <a href="https://codeforces.com/blog/entry/43615">345</a>, <a href="https://codeforces.com/blog/entry/47769">376</a>, <a href="https://codeforces.com/blog/entry/50613">401</a>, <a href="https://codeforces.com/blog/entry/54350">433</a>, <a href="https://codeforces.com/blog/entry/55201">441</a>, <a href="https://codeforces.com/blog/entry/57981">466</a>, <a href="https://codeforces.com/blog/entry/58229">469</a>, <a href="https://codeforces.com/blog/entry/61638">507</a>, <a href="https://codeforces.com/blog/entry/62440">516</a>, <a href="https://codeforces.com/blog/entry/65433">541</a>, <a href="https://codeforces.com/blog/entry/65768">5...
XVIII Open Olympiad in Informatics (Unrated, Online Mirror, IOI rules)
Announcement of XVIII Open Olympiad in Informatics - Final Stage, Day 1 (Unrated, Online Mirror, IOI rules)
70.
Invitation for ICPC Indonesia COMPFEST 12 Multi-Provincial Contest Online Mirror Hello Codeforces Community. I would like to invite you all for [ICPC Indonesia COMPFEST 12 Multi-Provincial Contest Online Mirror](https://codeforces.com/contests/1425). I am the Person In Charge of the event.
<img alt="compfestlogo" src="/predownloaded/88/b0/88b08f638596aeda8840ec8d7e5dd9944c17286a.jpg" style="float: right;height: 200.0px;margin: 10.0px;max-width: 100.0%;max-height: 100.0%;">
I want to thank:
- Faculty of Computer Science, The University of Indonesia, for providing guidance and support for the official event.
- Our committee: [user:hocky,2020-09-24], [user:julianfernando,2020-09-24], [user:faustaadp,2020-09-24], [user:dewa251202,2020-09-24], [user:MIsForMiracle,2020-09-24], [user:faishol27,2020-09-24].
- Our testers: [user:AMnu,2020-09-24], [user:stevenwjy,2020-09-24], [user:Yehezkiel,2020-09-24]
- [user:MikeMirzayanov,2020-09-24]: for giving us the opportunity to host this online mirror. Also, for Codeforces and Polygon platform.
The online mir...
Note: this contest is unrated.
71.
April Fools Day Contest 2022 With [user:Nickolas,2022-03-29] not writing a contest this year, [user:magnus.hegdahl,2022-03-29] and I have decided to take up this sacred duty :). We would like to invite everyone on Codeforces to the [contest: 1663]. Special thanks to [user:BucketPotato,2022-03-29] for volunteering to test this contest!
The 10th April Fools Day Contest will take place on [contest_time:1663]. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
In this round you'll be given several weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the contests of the past years: [2012](https://codeforces.com/contest/171), [2013](htt...
time earned on them), and it will be unrated. You can submit solutions in any
language allowed by
Announcement of April Fools Day Contest 2022
72.
Is It Rated?: what happened yesterday, the “unrated mentality” and how to handle round mishaps As most people know, in yesterday’s round [contest:1793], problem F coincided with a previous problem on Codeforces. A few months ago, a similar thing happened to [contest:1710], which also had an issue of coincided problems.
Of course, we know what happened next: [contest:1710] was unrated for div.1, while as it stands, this round will be rated as per [Mike’s latest blog post](https://codeforces.com/blog/entry/112709). I won’t elaborate more on that blog post; I assume you are familiar with Mike’s rationale.
I mulled over that decision for a while, and I’d like to raise a few points.
[cut]
First, let’s ask “is it fair?” Is it fair, for all parties involved, to keep the contest rated, or vice versa (to make it unrated)?
For the contest authors, it is undeniably unfair for them if the contest becomes unrated because of other factors. For those who got a good performance in the round, it would be unfair for their good performance to be discredited as well.
But on the ot...
Is It Rated?: what happened yesterday, the “unrated mentality” and how to
handle round mishaps, issue of coincided problems. Of course, we know what happened next:
[contest:1710] wasunrated for, participants of the round. Making the contest unrated would be a net negative
to the authors, but from the POV, that the round is unrated, myself included (even though I’m not a rated
participant). There are, vice versa (to make it unrated)?, For the contest authors, it is undeniably unfair for them if the contest becomes
unrated because of, In summary, if the round has been ruined, it is my belief that it should become
unrated. But as, Of course, we know what happened next: [contest:1710] was unrated for div.1,
while as it stands, This brings us to another issue: the **“unrated mentality”**, the belief that
the round isunrated, What prompts this response? A belief that the round will become unrated. And as
such, one easy way
73.
After-stream thoughts Hello again.
Next stream will start tomorrow (Wednesday) at 2pm CEST ([your timezone](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Errichto+Stream+%233&iso=20181003T14&p1=262)), solving problems from POI 22, round 1 ([link](https://szkopul.edu.pl/p/default/problemset_eng/oi/22)).
It will be on my [Youtube channel](https://www.youtube.com/channel/UCBr_Fu6q9iHYQCh13jmpbrg).
I did two streams this weekend that you can now find on my youtube [channel](https://www.youtube.com/channel/UCBr_Fu6q9iHYQCh13jmpbrg). The first with quite easy Codeforces problems that I solved from scratch (I haven't seen them before), also implementing them. The second one with a bit harder Topcoder problems that I've solved before, but I didn't necessarily remember the solution now — and for those I only described the solution, without implementation. The streams were fine but there are a lot of things to improve.
I wanted to see two things:
1. Can I stream? Am I able to try to sol...
I want to try streaming problem setting, maybe creating an unrated educational
round. The results
74.
Codeforces Round 886 (Div. 4) Hello Codeforces!
[user:mesanu,2023-07-20], [user:flamestorm,2023-07-20] and I are very excited to invite you to [contest:1850]! It starts on [contest_time:1850].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants of the fourth division_ wil...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, or you are an unrated participant/newcomer). We urge participants whose rating
is 1400+ not to, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 886 (Div. 4)
75.
Invitation to NUS CS3233 Final Team Contest 2024 Mirror (I'm too lazy to write a post so I copied [last year's](https://codeforces.com/blog/entry/114880), thanks [user:pooty,2024-04-14])
Hello, Codeforces community!
We are happy to invite you to participate in [National University of Singapore (NUS) CS3233 Final Team Contest 2024 Mirror](https://codeforces.com/contestInvitation/08b02f08a4a36a8e7c977b27e68e1e311f9d8d94) on [Monday, April 15, 2024, at 09:15 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20240415T1715&p1=236&ah=5). CS3233 is a course offered by NUS to prepare students in competitive problem solving.
**The contest is unofficial and will be held in Codeforces Gym.** Standard ICPC rules **(Unrated, ICPC Rules, Teams Preferred)** apply. **The contest is unrated. Note the unusual starting time.**
The problems are written and prepared by [user:user202729_,2024-04-14], [user:rama_pang,2024-04-14], [user:yz_,2024-04-14], [user:benson1029,2024-04-14], [user:HuaJun,2024-04-14], and [user:feeder1,2024-04-14].
...
**The contest is unofficial and will be held in Codeforces Gym.** Standard ICPC
rules **(Unrated
Announcement of NUS CS3233 Final Team Contest 2024
76.
Some notes on rating inflation ### Introduction
Recently there have been several suggestions that there is significant rating inflation now due to COVID-19. The typical hypothesis seems to be along the lines of:
> Because people stay at home more now, there is a lot of new inexperienced users who add a lot of rating to the system, pushing "old" users upwards without actual improvement.
A simplified and a bit more general hypothesis that I'm going to test:
> Because of the virus I'm gaining more rating than usual without working more.
But most of these comments are based on anecdotal evidence, which is not worth much.
I wanted to see if there is any truth to these claims.
Specifically, this blog is an implementation (although I modified the approach a bit) of the following [comment](https://codeforces.com/blog/entry/20638?#comment-601634) by [user:geckods,2020-04-15]:
[cut]
$~$
### Methodology
Let's define the "test period" and "control period".
...
unrated Technocup mirror. But I have provided the code, you can try other
periods and other period
77.
Codeforces Round #682 (Div. 2) Good Evening Codeforces! ^_^
This round is unrated; please read [this](https://codeforces.com/blog/entry/84595) to know why.
I invite you to participate in [Codeforces Round #682 (Div.2)](https://codeforces.com/contests/1438) taking place on [contest_time:1438]. The round, authored by [user:Anti-Light,2020-11-11] and me, is rated for users rated less than 2100, while other users can participate non-competitively.
The round features six problems, and you have 2 hours to solve them. There may, or may not, be an interactive problem; regardless, you should [know](https://codeforces.com/blog/entry/45307) how to deal with them.
I would, now, like to thank–
- [user:antontrygubO_o,2020-07-31] for coordination.
- [user:AwakeAnay,2020-07-31] and [user:AsleepAdhyyan,2020-07-31] for helping me solve one of the problems.
- [user:BRCode,2020-08-03] for making [3b1b-style](https://youtube.com/channel/UCSQmpb_K_I37JN-QLArZbFw) video editorials of the problems!
- [user:knightron00,...
This round is unrated; please read
[this](https://codeforces.com/blog/entry/84595) to know why.
Announcement of Codeforces Round 682 (Div. 2)
78.
How not to read problem statements I wanted to write super-harsh blog but then I decided to split it into educational part and whining part. This is whining part. To read some cool stuff go [here](https://codeforces.com/blog/entry/62730). This one will also be educational on a slightly different topic. And there will be A LOT of harsh stuff.
I'm not saying that I'm perfect. That round had some really bad problemsetting issues. Problem E was googleable, problem D had very weak tests against very stupid solution (so stupid that none of the authors and testers come up with it, moreover, it is so counter-intuitive that I don't know how so many people independently did it). In two constructive problems participants could look at jury's output, the feature of which I didn't know. And I'm sorry for these issues. BUT. [This comment](https://codeforces.com/blog/entry/62614#comment-466588) has very negative rating despite being so true. And no one are here to back me up. So I want to speak my truth as I always do.
Let me ac...
You can remember that once I made round unrated because I found the mistake in
authors solution. I
79.
AtCoder World Tour Finals 2022 Announcement (with Rated Mirrors) We will hold AtCoder World Tour Finals 2022.
List of Finalists:
<table border="1">
<tr align="center"><td>AtCoder ID</td><td>Codeforces ID</td><td>Advanced Years</td></tr>
<tr align="center"><td>[tourist](https://atcoder.jp/users/tourist)</td><td>[user:tourist,2023-09-06]</td><td>2019,2020,2021,2022</td></tr>
<tr align="center"><td>[ksun48](https://atcoder.jp/users/ksun48)</td><td>[user:ksun48,2023-09-06]</td><td>2019,2021,2022</td></tr>
<tr align="center"><td>[Benq](https://atcoder.jp/users/Benq)</td><td>[user:Benq,2023-09-06]</td><td>2020,2021</td></tr>
<tr align="center"><td>[Um_nik](https://atcoder.jp/users/Um_nik)</td><td>[user:Um_nik,2023-09-06]</td><td>2019,2020</td></tr>
<tr align="center"><td>[apiad](https://atcoder.jp/users/apiad)</td><td>[user:amiya,2023-09-06]</td><td>2019,2021,2022</td></tr>
<tr align="center"><td>[Stonefeang](https://atcoder.jp/users/Stonefeang)</td><td>[user:Radewoosh,2023-09-06]</td><td>2020</td></tr>
<tr align="center"><td>[ecnerwala](https...
strategies of participants, the Finals itself is unrated. Note that, unlike
other onsite competitions
80.
After a Round FAQ Every time a (rated) round ends, I always see the same questions from people who are new to Codeforces. So, here I made an FAQ that answers to these repeated questions. Please do provide the link to this blog when you want to answer to them.
#### Why is my rating still not updated yet?
Be patient. It takes a while (can be a few hours, or even more) to finalize things such as detecting cheats and confirming test results, or there can be other issues that need investigation. It won't be unrated unless they announced that it will be unrated.
#### My solution was hacked after contest, but why didn't my rank / rating change?
It is called _uphacking_, and it does NOT affect the standings nor rating changes. The score you gained from uphacked solution will remain. The hack tests will be added to the tests for practice submissions later, but there won't be any rejudges on already accepted solutions.
#### I got a system message that says that my submission coincides with other soluti...
other issues that need investigation. It won't be unrated unless they
announced that it will be, unrated unless they announced that it will be unrated. #### My solution was
hacked after contest, but
81.
Codeforces Round 871 (Div. 4) Hey, hi Codeforces!
It's [user:mesanu,2023-03-18], [user:flamestorm,2023-03-18] and me and we are very excited to invite you to [contest:1829]! It starts on [contest_time:1829].
We worked swiftly to tailor the problems for this contest, so we hope you will enjoy them! We tried to make the statements short, epic and concise.
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated, will be recalculated for all with initial ratings less than 1400 or you are an
unrated participant
Announcement of Codeforces Round 871 (Div. 4)
82.
March Summary ## Ratings
_It's always nice to see them growing._
- codeforces: 2311 + 21 = 2332
- atcoder: 2024 + 29 = 2053
- leetcode: 2701 + 81 = 2782
- dmoj: 2161 + 197 = 2358
- prepbytes: 1853 + 79 = 1932
## Contests
_A contest a day keeps mental health away._
- rated: 11
- unrated: 14
- fullsolve: 12
## Problems
_One downside of many contests is that you don't have time to upsolve properly._
- solved: 145
- upsolved: 5
- todo: 23
**Hardest problems that I solved in-contest:**
- [CF #779 E — Gojou and Matrix Game](https://codeforces.com/problemset/problem/1658/E)
- [ABC 245 G — Foreign Friends](https://atcoder.jp/contests/abc245/tasks/abc245_g)
- [CC Start 32 — Avoid Alternating](https://www.codechef.com/problems/AVOIDALT)
- [PB PT P5 — Kevin and his Operation](https://mycode.prepbytes.com/problems/bit-manipulation/KVOP)
**Easiest problems that I failed to solve in-contest:**
- [ARC 137 C — Distinct Numbers](https://atc...
- rated: 11 - unrated: 14 - fullsolve: 12
83.
2020 ICPC Graph Mining Challenge — Powered by Huawei: Battle of the Connected Brains [<img src="/predownloaded/aa/57/aa577c257884a5ae68792513c31d9f64fd7bff5f.png" align="right" style="height: 300px; margin: 10px 30px 20px;" alt="text"/>](https://challenge.icpc.global/)
**UPD:** You can predownload tests as an encrypted zip-archive by the links https://test1.codeforces.com/icpc-challenge-2020-tests.zip or https://test4.codeforces.com/icpc-challenge-2020-tests.zip (~80MB). The password is `64e00d81811bbc463e1e636af`.
Hello everyone!
<a href="https://u.icpc.global/" style="font-size: 15.0px;padding: 8.0px 14.0px;background-color: rgb(207, 56, 34);color: white;">Live broadcast</a>
Announcing the **ICPC Graph Mining Challenge**, Powered by Huawei and brought to you by [ICPC U](https://u.icpc.global/). Graphs are a powerful mechanism for representing many aspects of our daily lives, from mobile call routing to disease tracking. Answering various graph-related questions enables solutions to some of the most challenging, modern problems. The ICPC Challenge prese...
=20200627T14&p1=166&ah=3). This round is unrated for all participants. Day Zero
is a celebration of the, Both rounds are unrated for all participants
Announcement of ICPC Challenge 2020: Practice
Announcement of ICPC Challenge 2020
84.
April Fools Day Contest 2021 The contest is over; I hope you enjoyed it! The editorial is available [here](https://codeforces.com/blog/entry/89260).
---
The 9th April Fools Day Contest will take place on Thursday [April 1st](https://www.timeanddate.com/worldclock/fixedtime.html?day=1&month=4&year=2021&hour=17&min=35&sec=0&p1=166). This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
In this round you'll be given several weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the contests of the past years: [2012](http://codeforces.com/contest/171), [2013](http://codeforces.com/contest/290), [2014](http://codeforces.com/contest/409),...
solved problems and penalty time earned on them), and it will be unrated. You
can submit solutions in, time earned on them), and it will be unrated. You can submit solutions in any
language allowed by
Announcement of April Fools Day Contest 2021
85.
Codeforces Round 859 (Div. 4) Hello Codeforces!
[user:mesanu,2023-03-18], [user:flamestorm,2023-03-18] and I are very excited to invite you to [contest:1807]! It starts on [contest_time:1807].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants of the fourth division_ wil...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, or you are an unrated participant/newcomer). We urge participants whose rating
is 1400+ not to, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 859 (Div. 4)
86.
2020-2021 ICPC, NERC, Южный четвертьфинал (онлайн-трансляция, правила ICPC,
предпочтительно команды)
2020-2021 ICPC, NERC, Южный четвертьфинал (онлайн-трансляция, правила ICPC, предпочтительно команды) <img src="/predownloaded/15/fc/15fc6334d8410344121a28c96cdf1068f53f94d1.png" style="float:right; margin: 0 1em 1em 1em;"/>
Hello!
ICPC Southern and Volga Russian Regional Contest (Northern Eurasia) 2020 has ended on November 15.
This year the competition took place online.
108 teams competed, many of them received an invitation based on the results in Qualification Contest.
On
[contest_time:1468] will start online-mirror [contest:1468].
Hope you enjoy the problems. In this contest I play a role of Cheif Judge and the jury teams consists of ex-participants of ICPC
from Saratov and jury members from other cities:
[user:adedalic,2020-12-23],
[user:ashmelev,2020-12-23],
[user:BledDest,2020-12-23],
[user:DmitryKlenov,2020-12-23],
[user:DStepanenko,2020-12-23],
[user:elena,2020-12-23],
[user:KAN,2020-12-23],
[user:kuviman,2020-12-23],
[user:MikeMirzayanov,2020-12-23],
[user:pashka,2020-12-23],
[user:PavelKunyavskiy,2020-12-23],
Дмитрий Мещеряков,
Герман Наркайт...
Of course, the competition will be unrated. I ask the participants of the
official competition to
87.
Codeforces Round #849 (Div. 4) Hello Codeforces!
[user:flamestorm,2022-08-28], [user:SlavicG,2023-02-01], [user:MikeMirzayanov,2022-07-11] and I want to invite you to [contest: 1791].
It starts on [contest_time: 1791].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants...
initial ratings less than 1400 or you are an unrated participant/newcomer). We
urge participants, is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 849 (Div. 4)
88.
Codeforces Round #394 (Div. 2) Hi there!
Codeforces round #394 for the second division will take place at the time of [Tuesday, 31 January 17:35 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=31&month=1&year=2017&hour=17&min=35&sec=0&p1=166). Participants from the first division can compete out of competition. Contestants will have 2 hours and **6 problems** to solve.
<html>
<body>
<p>
<img src="http://codeforces.com/predownloaded/c0/ed/c0ed632751995e022101f7986487f528b63e876a.png" align=right hspace=20>
</p>
</body>
</html>
- Problems were developed by me (Vladislav Vishnevki) and Denis Anischenko ([user:altruist,2016-12-08]).
- Alexey Vistyazh ([user:netman,2016-12-08]) helped us as a contest coordinator.
- Aliaksandr Drapko ([user:sdryapko,2017-01-30]) and Alena Yaros were reading the statements carefully.
- Vlad Khala ([user:hapooo,2016-12-21]) tested the round.
- Olya Yakovchik drew amazing illustrations for the problems.
- Yuri Shilyaev ([user:hloya_ygrt,...
**UPD** Contest finished. It was decided to make round unrated, because
codeforces is unstable now
Announcement of Codeforces Round 394 (Div. 2)
89.
Unofficial Div 4 Round #2 Hello Codeforces!
------------------
[user:SlavicG,2020-10-01] and I are glad to invite you to Unofficial Div 4 Round #2. Which will take place [this Wednesday at 14:35 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Unofficial+Div+4+Round+2&iso=20201125T1430&p1=%3A&ah=2) (The round is over now, but you can still participate virtually). The round will not be rated for any participants since it is unofficial.
Contest link: https://codeforces.com/gym/102873
You will be given six tasks and two hours to solve them.
The problems were created and prepared by [user:ssense,2020-11-01] and [user:SlavicG,2020-10-01] for users with a rating range from 0 to 1400 but anyone is welcome to participate in the round!
We want to thank everyone who was involved in the round preparation:
[user:Errichto,2020-11-22] for thorough testing and publishing this round on the gym.
Also, after the contest [user:Errichto,2020-11-22] will post videos about this contest and the respon...
Even though the contest is unrated, we believe it is an excellent way of
practice, especially for
Announcement of Unofficial Div 4 Round #2 by ssense SlavicG
90.
Insights from testing and preparing contests, and why problemsetting trends need to change I've been involved with testing a lot of Codeforces contests and coordinating contests for my uni, and have seen various kinds of issues crop up. However, I was able to come up with a stable system for my uni contests that helped make the experience as educational and error-free as possible, and I have found the lack of some of those things to be the main reason behind issues faced by Codeforces contests.
Given that it takes months to get a round ready, it is better to be more careful than necessary compared to getting your round unrated or having bad feedback in general.
I'd like to thank [user:Ari,2023-01-26], [user:null_awe,2023-01-26] and [user:prabowo,2023-01-26] for reviewing the blog and discussing more about problem-setting.
The current Codeforces contest guidelines are [here](https://docs.google.com/document/d/e/2PACX-1vRhazTXxSdj7JEIC7dp-nOWcUFiY8bXi9lLju-k6vVMKf4IiBmweJoOAMI-ZEZxatXF08I9wMOQpMqC/pub) for problem-setters and [here](https://docs.google.com/document/d...
compared to getting your round unrated or having bad feedback in general., making the contest unrated immediately.
91.
My winning theory in IOI 2018 & 2019 — Why I won 2 golds in IOI Dear Codeforces community.<br />
According to [IOI 2019 Results](http://stats.ioinformatics.org/results/2019), I got the 25th place and got successful gold medals twice in a row.<br />
Although it was pretty close to the gold-medal border (only 6.14pts / 600 difference) and it was lower performance than IOI 2018, which I participated when I was orange in Codeforces, I had many chances to get more points in this IOI, even for top 10. Since there are not so many people who have got two gold medals in IOI (and there were many requests like "I want [user:E869120,2019-08-14] to talk about how to get gold in IOI" like [this comment](https://codeforces.com/blog/entry/66909?#comment-510127) and [this comment](https://codeforces.com/blog/entry/66909?#comment-513129)). I want to write something about IOI, which may be useful for people who will participate in IOI next year and also some years later.<br />
<br />
<br />
### A. First of all
At...
unrated, but in IOI the round cannot be unrated. So, your **flexibility** —
ability to respond to the
92.
April Fools Day Contest 2021 — ZS Edition Hi everyone,
April Fools is near and as usual we have an [April Fools Day Contest](https://codeforces.com/blog/entry/88840) on Codeforces this year. In addition to that, I usually try to host some form of mini April Fools Contest for my friends every year (or almost every year).
This year, I am trying to host a bigger April Fools Day contest than usual and I invite everyone to participate! In view of the April Fools contest on Codeforces, the round will begin at [31 March 10pm (GMT+8)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=April+Fools+Day+Contest+2021+%28ZS%29&iso=20210331T22&p1=122) and lasts for exactly $24$ hours (and thus it will end ~35 minutes before the CF April Fools round).
The contest will consist of several unusual tasks, and I hope that everyone will at least find something interesting. The problems will not be sorted by increasing order of difficulty (if the word difficulty is even applicable), so it is **highly advisable** to read (and try!)...
is **not** an offical Codeforces round and thus is obviously **unrated**.
Announcement of April Fools Contest 2021 Archive (ZS)
93.
Codeforces Round #790 (Div. 4) Hello Codeforces!
[user:SlavicG,2022-05-09], [user:mesanu,2022-05-09], [user:MikeMirzayanov,2022-05-09], [user:Errichto,2022-05-09], and I welcome you to [contest:1676]. It starts on [contest_time:1676].
The format of the event will be the same as before:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted partic...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated, with initial ratings less than 1400 or you are an unrated
participant/newcomer). We urge
Announcement of Codeforces Round 790 (Div. 4)
94.
Codeforces Round 640 (Div. 4) _I almost copied my previous blog post to separate two discussions: about Div. 4 in general and about Round 640.
Please, visit [this blog post](/blog/entry/77028) to discuss Div. 4 rounds._
Hello Codeforces!
Yes, it is not a mistake I decided to run the first Div. 4 round: [contest:1352]! It starts on [contest_time:1352].
The format of the event will be identical to Div. 3 rounds:
* 5-8 tasks;
* ICPC rules with a penalty of 10 minutes for an incorrect submission;
* 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
* after the end of the open hacking phase, all solutions will be tested on the updated set of tests and the ratings recalculated
* by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are unrated participant/newcomer).
I urge participants whose rating is 1400+ not to register new accounts for the purpose of na...
rating will be recalculated for all with initial ratings less than 1400 or you
areunrated participant, your rating is less than 1400 (or you are a newcomer/unrated), then the round
will be rated for you.
Announcement of Codeforces Round 640 (Div. 4)
95.
Codeforces Round #697 (Div. 3) Hello, Codeforces! Were you afraid of the lack of contests? We also!
**Unfortunately, due to technical problems, the round is declared unrated. You can continue to solve problems, but the results of the current round will not affect your rating. We are sorry for this situation.**
\<almost-copy-pasted-part\>
Hello! [Codeforces Round #697 (Div. 3)](https://codeforces.com/contest/1475) will start at [contest_time:1475]. You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially.
The round will be hosted by rules of educational rounds (extended ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over....
**Unfortunately, due to technical problems, the round is declared unrated. You
can continue to
Announcement of Codeforces Round 697 (Div. 3)
96.
Statistics of New Year Magic #### Introduction
New Year's traditional masquerade of colors and ranks is going to end pretty soon, and before it goes away, I decided to download a snapshot of everyone's true ratings and current handle colors to see how everyone's using the feature. I regret that I only have one snapshot; I only managed to push myself to finish this today. It would have been really cool to see how people's usage of the feature has evolved — perhaps an initial surge of masquerading as a nutella, then slowly coming to one's senses and opting for something milder?
Data was collected on January 9th, at about 01:00 UTC. I collected the data by scraping the pages of the "rating" tab (sorry for making a lot of requests!) — the table contains people's actual ratings, and by looking at the title-text of people's handles, I could also get their possibly-magicked ranks. I only included the active people because it was already taking a lot of time, and I believe we got most of the interesting ...
believe we got most of the interesting parts anyway. Sadly this excludes
magic-usingunrated and
97.
2018 KAIST RUN Spring Contest (GYM) Hello Codeforces!
In [2018/05/26 21:30 Korea Standard Time (UTC+9)](https://www.timeanddate.com/worldclock/fixedtime.html?day=25&month=5&year=2018&hour=15&min=30&sec=0&p1=166) we will hold an online mirror of 2018 KAIST RUN Spring Contest. This is an annual individual contest held by KAIST's algorithm club RUN.
Problems are available in English, and you should individually solve 11 problems in 5 hours. [The problems will be prepared in Gym](http://codeforces.com/contests/101806), so this contest is unrated. Grading rules are ICPC-style. There are no prizes in this contest, but if any top scorers come to KAIST, we will bring you to our favorite restaurants or pubs ( ͡° ͜ʖ ͡°)
This online mirror might not reflect the onsite contest fully, due to some technical limits. For example, the grading rules in main contests were IOI-style, every problems were 100 points with subtasks and we had no penalties, but we had some difficulties implementing it on CF environment :/
Problems w...
problems will be prepared in Gym](http://codeforces.com/contests/101806), so
this contest isunrated
98.
Your true self **TL;DR stop making new accounts just to post blogs and post it on your main.**
Hello everyone!
I know it has been a while since I ever post a blog. I'm lazy ok? Today I want to tell you what went pretty bad recently: The existence of **alts**.
There are many type of alts which is being used for different stuffs, but let's put it in a side and talk about the most annoying type for me. Yeah, those unrated alts that appears everywhere, from recent blogs to comment sections.
If I am not wrong then every 1-2 days there would be an alt like that appear and post something like: Asking to be better at topics, talking about CP in india, or other stuffs. But what occur the most? Those who "catch" cheaters.
When **EVERY SINGLE CONTEST** that ends there would appear a blog that says "Cheater EXPOSED in Codeforces round #XYZ!" or "Google Kickstart round M code LEAKED!" from a random alt created shortly ago, drop a bunch of comments, and then some continue doing their "good" ...
and talk about the most annoying type for me. Yeah, those unrated alts that
appears everywhere, from, make an impact on cheaters (They are unrated, and yes, there are too many
cheaters), but they make
99.
Educational Codeforces Round 8 Hello, Codeforces!
Educational Codeforces Round 8 will take place on [19 February 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+8&iso=20160219T1500) for the first and the second divisions. You can read about educational rounds [here](http://codeforces.com/blog/entry/21496) and [here](http://codeforces.com/blog/entry/21565). I hope that the high density of contests on Codeforces will not startle you and you will participate in ER8.
\<The phrase about simple problems is added in the end\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.
It seems that it is har...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 8
100.
Codeforces Round 898 (Div. 4) Hello Codeforces!
[user:flamestorm,2023-09-20], [user:MikeMirzayanov,2022-07-11] and I want to invite you to [contest: 1873].
It starts on [contest_time: 1873].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants of the fourth division_ wi...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, or you are an unrated participant/newcomer). We urge participants whose rating
is 1400+ not to, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 898 (Div. 4)
101.
Codeforces Round 928 (Div. 4) [user:mesanu,2024-02-18], [user:SlavicG,2024-02-18] and I are very excited to invite you to [contest:1926]! It starts on [contest_time:1926]. We would also like to give a very special thanks to the efforts of [user:MikeMirzayanov,2024-02-19] and [user:Vladosiya,2024-02-19], who helped significantly with the preparation of the round!
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purp...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 928 (Div. 4)
102.
SnackDown 2021 Grand Finale, Parallel Contest & Closing Ceremony It’s finally time for one of the biggest events in the competitive programming world. The SnackDown ‘21 Grand Finale is here.
The entire Grand Finale event is scheduled to be completed in two days — January 8 (Saturday), and January 9 (Sunday).
### For the Finalists
All the information has been shared over email, but summarising — The Grand Finale will be spread over two days and will be a closed event accessible only to the finalists, and a few invited guests. The SnackDown 2021 Final contest will be held on Jan 9th between 6:30 — 10:30 PM (IST).
For the last time for this SnackDown, meet the panelists!
<ul>
<li>Contest Admins: Anton [user:antontrygubO_o,2022-01-08] Trygub and Yahor [user:mhq,2022-01-08] Dubovik</li>
<br>
<li>Head Admin: Alex [user:Um_nik,2022-01-08] Danilyuk</li>
<br>
<li>Testers: Ashley [user:errorgorn,2022-01-08] Khoo and Andrew [user:ecnerwala,2022-01-08] He </li>
<br>
<li>Setters: Federico [user:dario299...
SnackDown Final Parallel Unrated Contest scheduled for January 9, 2022, 6:30
PM — 10:30 PM (IST). The, [SnackDown Final Parallel Unrated Contest](https://www.codechef.com/SNCKFP21)
scheduled for January 9, 2022
103.
Mirror of Bubble Cup 14 Finals on Codeforces Hello, Codeforces!
[Microsoft Development Center Serbia](https://www.microsoft.com/en-rs/mdcs) is thrilled to announce the finals of the **14th edition of Bubble Cup competition!** Bubble Cup is an international, **ICPC-style team contest** aimed at university and high school students.
Contest will take place on [Saturday, 9th of October at 10AM CEST](https://www.timeanddate.com/worldclock/fixedtime.html?day=9&month=10&year=2021&hour=10&min=0&sec=0&p1=35), in online format. Winners will be announced at the closing ceremony. You can find more info on the [BubbleCup website](https://www.bubblecup.org/).
Just like the previous editions, this final will be followed by an online mirror competition on Codeforces. Mirror will take place on the same day about an hour after the start of the finals — [contest_time:1599]. Contest will last for **4 hours** and **ICPC rules** will be applied. It will be a comp...
Both contests will be **unrated**, due to the format and the length of the
mirror being dissimilar
104.
Codeforces Round #827 (Div. 4) Hello Codeforces!
[user:mesanu,2022-06-12], [user:flamestorm,2022-10-11], [user:MikeMirzayanov,2022-06-12] and I are glad to invite you to [contest:1742]! It starts on [contest_time:1742].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants o...
initial ratings less than 1400 or you are an unrated participant/newcomer). We
urge participants whose, is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 827 (Div. 4)
105.
Educational Codeforces Round 20 Hello Codeforces!
On [April 28, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+20&iso=20170428T1805&p1=166) will be held Educational Codeforces Round 20.
Series of Educational Rounds continue being held as Harbour.Space university initiative! You can read the details about the cooperation between Harbour.Space and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
Here is the special message from Harbour.Space University for **girls from India**:
<b><i>Harbour.Space University offers a unique opportunity to win a FULL SCHOLARSHIP for #womenintechIndia and join our amazing Data Science, Computer Science or Cyber Security Master's Programme in Barcelona, Spain!
Follow [this link](http://in.harbour.space/data-science/scholarship-women-in-tech-india/) to complete the application form.</i></b>
<div style="text-align:center"><img src ="http://codeforces.com/predownloaded/b5/00/b500f462d444675...
The round will be **unrated** for all users and it will be held with extented
ACM ICPC rules. After
Announcement of Educational Codeforces Round 20
106.
Codeforces Round #721 (Rated for Div2) Hi, Codeforces!
I'm glad to invite you to take part in [Codeforces Round #721 (Div. 2)](https://codeforces.com/contests/1527), which will take place on [contest_time:1527]. The round will be **rated for the participants with a rating lower than 2100**. Participants from the first division are also welcomed to take part in the competition but it will be unrated for them.
You will be given **2 hours** to solve **5-6 problems**. Problems were created by members of Club of Programmers IIT (BHU)- [user:rivalq,2021-05-18], [user:sharabhagrawal25,2021-05-18], [user:loud_mouth,2021-05-18], [user:DenOMINATOR,2021-05-18], [user:Bignubie,2021-05-19], [user:mallick630,2021-05-18],
[user:shikhar7s,2021-05-18], [user:CoderAnshu,2021-05-19] and Me.
Huge thanks to those who helped make this round possible:
- [user:Aleks5d,2021-05-18] and [user:KAN,2021-05-18] for their excellent coordination and for providing priceless feedback during contest creation.
- [user:1-gon,2021-05-18], [u...
part in the competition but it will be unrated for them.
Announcement of Codeforces Round 721 (Div. 2)
107.
2015-2016 ACM-ICPC, NEERC, Southern Subregional Contest (Online Mirror, ACM-ICPC Rules, Teams Preferred) <img src="http://assets.codeforces.com/images/neerc-southern-2015-small.png?1" style="margin:0 1em 1em 1em; float:right;"/>
<b>You may print PDF-statements: http://assets.codeforces.com/statements/589.pdf</b>
Recently 2015-2016 ACM-ICPC, NEERC, Southern Subregional Contest has been finished. On behalf of jury and hosts I congratulate winners and advancers to the semifinals. Prize places are (horray!):
* 1 place: Nizhny Novgorod State University #1 (Vladislav [user:vepifanov,2015-10-16] Epifanov, Nikolay [user:KAN,2015-10-16] Kalinin, Mikhail [user:mike_live,2015-10-16] Krivonosov)
* 2 place: Innopolis University #1 (Evgeniy [user:savinov,2015-10-16] Savinov, Sergey [user:sokian,2015-10-16] Kiyan, Alexander [user:map,2015-10-16] Mashrabov)
* 3 place: Saratov State University #1 (Edvard [user:homo_sapiens,2015-10-16] Davtyan, Vitaliy [user:kuviman,2015-10-16] Kudasov, Danil [user:dans,2015-10-16] Sagunov)
On <a href="http://timeanddate.com/worldclock/fixedtime.html?day=17&...
For sure, it will be unrated contest. We recommend you to take part in teams. I
think, the contest
108.
LGMSniper.com: See which LGMs you have beaten! LGM Sniper
==================
I just created a cool CF tool called [LGM Sniper](https://wumbogames.com/CompetitiveProgramming/LGMSniper). It looks at scoreboard data from every Div1 and Div1+Div2 round ever and tells you which LGM's you have beaten, how many times you have beaten them, and which rounds you beat them in. You can also compare yourself to your friends to see which one of you wins more! If you want to compare yourself with some friends, check the 'show ex-lgms' box and enter the friend you want to compare to as Handle #2, and they will show up on the bottom.
You can try it out for yourself at [lgmsniper.com](https://wumbogames.com/CompetitiveProgramming/LGMSniper), or in the competative programming section of [Wumbo Games](https://wumbogames.com/), if you would prefer. Tooltips show the name of the rounds you won in (hover your mouse over the checkmark).
If you find any interesting facts or have suggestions for how I could improve the tool, let me know in the co...
Codeforces to make a round unrated using this tool because it doesn't actually
query Codeforces except for, a round unrated using this tool because it doesn't actually query Codeforces
except for when I
109.
Educational Codeforces Round 7 Hello, Codeforces!
Educational Codeforces Round 7 will take place on [10 February 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+7&iso=20160210T1500) for the first and second divisions. You can read about educational rounds [here](http://codeforces.com/blog/entry/21496) and [here](http://codeforces.com/blog/entry/21565).
\<This paragraph was modified last time\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.
\</This paragraph was modified last time\>
Thanks a lot to Aleksa Plavsic [user:allllekssssa,2016-02-08] who suggested the problems D, E and Ivan Po...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 7
110.
Educational Codeforces Round 51 [Rated for Div. 2] On [contest_time:1051] [contest:1051] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extented ACM ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Roman [user:Ajosteen,2018-09-19] Glazov, Ivan [user:BledDest,2018-09-19] Androsov and me.
Good luck to all participants!
Our friends at Harbour.Sp...
possible. The round can become unrated, we are discussing this at the moment.
Announcement of Educational Codeforces Round 51 (Rated for Div. 2)
111.
Codeforces Round 937 (Div. 4) Hej, Codeforces!
[user:mesanu,2024-02-18], [user:SlavicG,2024-02-18] and I are very excited to invite you to [contest:1950]! It starts on [contest_time:1950].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants of the fourth division_ will be...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 937 (Div. 4)
112.
Codeforces Round #835 (Div. 4) Hello Codeforces!
[user:mesanu,2022-06-12], [user:flamestorm,2022-10-11], [user:MikeMirzayanov,2022-06-12] and I are glad to invite you to [contest:1760]! It starts on [contest_time:1760].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants o...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 835 (Div. 4)
113.
Educational Codeforces Round 25 Hello Codeforces!
On [July 16, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+25&iso=20170716T1805&p1=166) Educational Codeforces Round 25 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the [blog post](http://codeforces.com/blog/entry/51208).
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were prepared by Ivan [user:BledDest,2017-07-15] Androsov and me.
Good luck to all participants!
UPD: The editorial can be found [here](http://codeforces.com/blog/entry/5...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 25
114.
I was wrongly flagged as a cheater in the last div2 round 
Today, I've received system messages that my submissions on problem A and C from last division 2 round (round #738) coincides with someone else, and got all my submissions skipped.
I compete on sublime text, and do not use any online editors such as ideone.
I'm guessing the reason my submissions got flagged is due to how simple solutions to problem A and C are.
These two are the submissions to problem A which the system thinks coincide. [submission:125936660] [submission:125936386]
Comparing them with the codes from the editorial and jiangly, they're almost similar to our codes. I think most people came up with a similar approach, so these similarities cannot be an evidence that we cheated. [Editorial](https://codeforces.com/blog/entry/93898) [submi...
- The round is unrated for me
115.
Codeforces Round #817 (Div. 4) Hello Codeforces!
[user:flamestorm,2022-08-28], [user:MikeMirzayanov,2022-07-11] and I want to invite you to [contest:1722].
It starts on [contest_time:1722].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants of the fourth division_ will...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 817 (Div. 4)
116.
Educational Codeforces Round 19 Hello Codeforces!
On [April 15, 17:35 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+19&iso=20170415T1735&p1=166) will be held Educational Codeforces Round 19.
This Educational Round is held as Harbour.Space university initiative. It's the second round supported by Harbour.Space. You can read the details about the cooperation between Harbour.Space and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
<div style="text-align:center"><img src ="http://codeforces.com/predownloaded/b5/00/b500f462d444675afcbf458ed4d396607277b544.png" /></div>
Some educational programs in Harbour.Space are interesting for most Codeforces users. One of them is Data Science Program.
Here is few words from Sergey Nikolenko, Harbour.Space lecturer and Senior Researcher, Steklov Institute of Mathematics at St. Petersburg Russia.
<iframe width="560" height="315" src="https://www.youtube.com/embed/A2hw_b_PLzk" frameborder="...
The round will be **unrated** for all users and it will be held with extented
ACM ICPC rules. After
Announcement of Educational Codeforces Round 19
117.
Codeforces Round #233 Editorial Please write here if you had written some comments about any suggestions or questions on the announcement. There are a bunch of notification emails but I couldn't read most of them :(
Here are the final top 100 : [Div1](https://www.google.co.kr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CCsQIDAA&url=http%3A%2F%2Fwebcache.googleusercontent.com%2Fsearch%3Fq%3Dcache%3A1RF3QO-_JXoJ%3Acodeforces.com%2Fcontest%2F398%2Fstandings%2B%26cd%3D1%26hl%3Dko%26ct%3Dclnk%26gl%3Dkr&ei=u6YUU9-HGYXEkgWNqIHICA&usg=AFQjCNFkij08MpvPcSG2HI4LDa_FK0COLA&sig2=RI29yARCrh2DimTBQSmfGw&bvm=bv.61965928,d.dGI), [Div2](https://www.google.co.kr/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CC0QIDAA&url=http%3A%2F%2Fwebcache.googleusercontent.com%2Fsearch%3Fq%3Dcache%3ARm3K-hziD8QJ%3Acodeforces.com%2Fcontest%2F399%2Fstandings%2B%26cd%3D1%26hl%3Dko%26ct%3Dclnk%26gl%3Dkr&ei=sKYUU6-KFMbQlAXtzIHABQ&usg=AFQjCNHwmP4LqOrHIo0ELTh9cXnhmY0jWw&sig2=5lJH4564SjPuel1PElvTdQ&bvm=bv.61965928,d.dGI). Congrats to th...
First of all, we are sorry to make this round unrated. This is an unexpected
incident, and I
Tutorial of Codeforces Round 233 (Div. 1)
Tutorial of Codeforces Round 233 (Div. 2)
118.
2022-2023 ICPC, NERC, Southern and Volga Russian Regional Contest [Online Mirror, ICPC Rules] Hello Codeforces!
The Southern and Volga Russian Regional Contest was held in Saratov State University on 22nd of November. This contest was used to qualify the teams from Southern Russia and Volga region to the Northern Eurasia Finals.
On [contest_time:1765], we will conduct the online mirror of this contest. It will last for *5 hours* and is best suited for *teams of three people*, although it is not forbidden to participate in teams of smaller/larger size. The mirror will use ICPC rules, the same as the offline contest.
I would like to express my gratitude to all other jury members: [user:awoo,2022-11-23], [user:Neon,2022-11-23], [user:vovuh,2022-11-23], [user:adedalic,2022-11-23], [user:DmitryKlenov,2022-11-23], [user:dmitryme,2022-11-23], [user:DStepanenko,2022-11-23], [user:elena,2022-11-23] and [user:kuviman,2022-11-23]. Also, big thanks to the contest testers: [user:IlyaLos,2022-11-23], [user:Oleg_Smirnov,2022-11-23], [user:I_remember_Olya_ashmelev,2022-11-23], [user:p...
Of course, the contest will be *unrated*.
119.
Educational Codeforces Round 31 Hello Codeforces!
On [October 27, 17:05 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?day=27&month=10&year=2017&hour=17&min=5&sec=0&p1=166) Educational Codeforces Round 31 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the [blog post](http://codeforces.com/blog/entry/51208).
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 problems** and **2 hours** to solve them.
The problems were prepared by Ivan [user:BledDest,2017-10-26] Androsov, Vladimir [user:0n25,2017-10-26] Petrov, Alexey [user:Perforator,2017-10-26] Ripinen, Mike [user:MikeMirzayanov,2017-10-26] ...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 31
120.
Mirror of Bubble Cup 13 Finals on Codeforces Hello, Codeforces!
Hope you're all safe and well.
[Microsoft Development Center Serbia](https://www.microsoft.com/sr-latn-rs/mdcs) is thrilled to announce the finals of the **13th edition of Bubble Cup competition**!
Bubble Cup is an international, **ACM-style team contest** aimed at university and high school students.
Contest will take place on [Sunday, 4th of October at 11AM CEST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Bubble+Cup+13+Finals&iso=20201004T11&p1=35&ah=3), virtually. Live results will be available on the official Bubble Cup website (results will be frozen during the last 45 minutes of the competition). Winners will be announced at the closing ceremony. You can find more info on the [BubbleCup website](https://www.bubblecup.org/).
Just like the previous editions, this final will be followed by an online mirror competition on Codeforces. Mirror will take place on [Mon...
The contest will be unrated. The reason for this is because rules of this
contest are not common
Announcement of Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 1]
Announcement of Bubble Cup 13 - Finals [Online Mirror, unrated, Div. 2]
121.
CEOI 2019 Mirror [The 26th Central European Olympiad in Informatics](https://ceoi.sk/) will take place in Bratislava, Slovakia, during **July 23rd-29th 2019**. The most gifted high school students from 13 countries will have the opportunity to prove their knowledge and skills in informatics.
Codeforces will organise the online mirror for this year's competition. The online mirrors will take place after the finish of each of the 2 competition days, having the same scoring format.
The online mirror schedules are the following:
- [contest_time:1192]
- [contest_time:1193]
**Contest format**
- The contest will be unrated for all users.
- You will have to solve 3 tasks in 5 hours.
- There will be full feedback throughout the entire contest.
- The scoreboard will be hidden until the end of the contest.
- The tasks will have partial scoring. The maximum score for each problem will be 100 points.
- Among multiple submissions only the one that achieves the maximum score is counted towards t...
- The contest will be unrated for all users. - You will have to solve 3 tasks
in 5 hours. - There
Announcement of CEOI 2019 day 1 online mirror (unrated, IOI format)
Announcement of CEOI 2019 day 2 online mirror (unrated, IOI format)
122.
Educational Codeforces Round 30 Hello Codeforces!
On [October 12, 17:05 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?day=12&month=10&year=2017&hour=17&min=5&sec=0&p1=166) Educational Codeforces Round 30 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the [blog post](http://codeforces.com/blog/entry/51208).
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 problems** and **2 hours** to solve them.
The problems were prepared by Ivan [user:BledDest,2017-10-11] Androsov, Vladimir [user:0n25,2017-10-11] Petrov, Mike [user:MikeMirzayanov,2017-10-11] Mirzayanov and me.
Good luck to all partic...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 30
123.
Educational Codeforces Round 24 Hello Codeforces!
On [June 29, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=29&month=6&year=2017&hour=18&min=5&sec=0&p1=166) Educational Codeforces Round 24 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours 15 minutes** to solve them.
The problems were prepared by Mikhail [user:PikMike,2017-06-28] Piklyaev, Alexey [user:Perforator,2017-06-28] Ripinen and me.
Good luck to all participants!
I also have ...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 24
124.
Community-prepared testing rounds Since the two failures of the contests last weekend, a lot of people have expressed that they want to help Codeforces in some way, but there isn't much many of us can actually do about the system. At the same time, there have also been a lot of (reasonable) requests for a testing round before round 656. So let's put those two together. Why don't we set some potential testing rounds? Maybe they should be rated, maybe they shouldn't, but in any case, they should be interesting enough to draw in participants like normal rounds do. It's probably not a good idea to "sacrifice" rounds not rated for Div. 1, as some have suggested, because that still wastes the efforts of the setters. So what I'm suggesting is that we prepare rounds with the specific intent of them being testing rounds.
Some advantages of this system:
- If these rounds are unrated, there's much less pressure for original/novel problems (and probably fewer problems will be rejected), so more of these rounds will be able t...
- If these rounds are unrated, there's much less pressure for original/novel
problems (and probably
Announcement of Testing Round #XVII
125.
Invitation to CodeChef May Starters 40 (Rated for Div 2, 3 & 4) — 26th May ( Unrated ) We invite you to participate in CodeChef’s [Starters 40](https://www.codechef.com/START40?utm_source=codeforces_blog&utm_medium=organic&utm_campaign=START40), this Thursday, 26th May, will be an unrated round.
Time: [8 PM — 11:00 PM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=CodeChef%20Starters%2040&iso=20220525T20&p1=44&ah=3)
Joining us on the problem setting panel are:
- Setters:Tejas [user:tejas10p,2022-05-24] Pandey, Utkarsh [user:Utkarsh.25dec,2022-05-24] Gupta, Mohammad Lutfar [user:rifatrraazz,2022-05-24] Rahman RIFAT, Sai Suman [user:saisumanchitturi,2022-05-24] Chitturi, Yash [user:kulyash,2022-05-24] Kulkarni, Sahil [user:still_me,2022-05-24] Tiwari, Hrishikesh [user:hrishik85,2022-05-24] Kelker, Kerim [user:Kerim.K,2022-05-24] Kochekov
- Testers: Utkarsh [user:Utkarsh.25dec,2022-05-24] Gupta, Satyam [user:satyam_343,2022-05-24]
- Statement Verifier:Nishank [user:IceKnight1093,2022-05-24] Suresh
- Editorialists: Devendra [user:Drag...
Invitation to CodeChef May Starters 40 (Rated for Div 2, 3 & 4) — 26th May (
Unrated ), problem set will be unfair and hence, we have decided to make tomorrow's
contestunrated., unrated round.
126.
The 2019 China Collegiate Programming Contest Harbin Site (Online Mirror) in Gym Hello, Codeforces!
The China Collegiate Programming Contest (CCPC) is a competitive programming contest series for college students in China, organized by the CCPC Committee, which consists of coaches of the competitive programming teams of Chinese universities. It started in 2015, and this year is the 5th edition of CCPC. There are 4 onsite CCPC contests this year, including three regional contests in Qinhuangdao, Harbin and Xiamen, as well as the CCPC Final in Beijing. Many Chinese universities use CCPC as an opportunity to practice before the ICPC regionals.
The 2019 CCPC Harbin Site has recently ended on October 13 in Northeast Forestry University. A total of 272 teams, most of whom were selected from the preliminary online contest, took part in the official onsite contest in Harbin. The problems for this contest were mostly prepared by retired ICPC participants of Zhejiang University, and the head judge was me.
We are glad to invite you to participate in its online mirro...
This contest uses ACM-ICPC rules and of course, it is unrated. Team
participation is recommended
Announcement of The 2019 China Collegiate Programming Contest Harbin Site
127.
Educational Codeforces Round 12 Hello, Codeforces!
Note! The day of the contest here was wrong. Now it's fixed.
Educational Codeforces Round 12 will take place on [20 april 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+12&iso=20160420T1500) for the first and the second divisions.
<Advertising space is still available>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.
It seems that it is harder to invent interesting simple problems (like A and B) than difficult ones. So don't be afraid to suggest interesting simple or very simple tasks (of course the difficult tasks are also needed). Plea...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 12
128.
Educational Codeforces Round 6 Hello, Codeforces!
Educational Codeforces Round 6 will take place on [21 January 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+6&iso=20160121T1500) for the first and second divisions. You can read about educational rounds [here](http://codeforces.com/blog/entry/21496) and [here](http://codeforces.com/blog/entry/21565).
\<Your Ad Could Be Here\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.
\</Your Ad Could Be Here\>
Thanks a lot to Aleksa Plavsic [user:allllekssssa,2016-01-20] who suggested several problems, two of them you will see on the round (the p...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 6
129.
random quotes Oh hi! Welcome to 24 random quotes!
I'm a competitive programmer, but I'm also pretty much a fan and often visit here to see some recent actions. I have a pretty unusual hobby: Collecting some sentences from blogs and comments and saving them as pictures, which I could use later for memes. Later I realized that I couldn't use it that much and after 4 years, it became a collection of well, memories. So I had the idea of sharing some of it with you guys for nostalgia! Most of them are light-hearted, and all of them are pretty memorable in my mind.
If you are an experienced member here you might realize some of them, so I will make it a challenge: Guess where this is from! (No prizes sadly) The spoiler to the link of the comment/blog and my personal opinion (or s/p) will be right below the quote.
Anyways, enjoy.
> If newcomers find it confusing, then that's their bugaboo
<spoiler summary="s/p">
[Link](https://codeforces.com/blog/entry/91480#comment-800196)
Still rem...
during the time we were figuring out if we really have to make it unrated. I
got something like 50
130.
Codeforces Round #806 (Div. 4) Hello Codeforces!
[user:SlavicG,2022-07-07], [user:flamestorm,2022-07-07], [user:MikeMirzayanov,2022-07-11] and I want to invite you to [contest:1703].
It starts on [contest_time:1703].
The format of the event will be identical to Div. 3 rounds:
- 5-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).
We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.
Only _trusted participants o...
is less than 1400 (or you are a newcomer/unrated), then the round will be
rated for you.**, rating will be recalculated for all with initial ratings less than 1400 or you
are anunrated
Announcement of Codeforces Round 806 (Div. 4)
131.
Codeforces Round #415 Hello everyone!
This Saturday [May 20, 21:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=20&month=5&year=2017&hour=21&min=05&sec=0&p1=166) rated Codeforces Round #415 takes place.
As for our previous round 384, the problems were set by Kiril [user:kefaa,2017-05-16] Gulin and Yura [user:hloya_ygrt,2017-05-16] Shilyaev. And this time Daniil [user:Melnik,2017-05-16] Melnichenko joined us! Many thanks to coordinator Alex [user:netman,2017-05-16] Vistyazh for help in preparations of the round, and also to Mike [user:MikeMirzayanov,2017-05-16] Mirzayanov for Codeforces and Polygon systems.
While everyone is waiting for second half of "SKAM" series season, we offer you to solve problems, main characters of which would be stunning girl Noora and well-known to you from [problem:794F] hacker Leha!
As always, participants of both divisions will be given 5 problems and 2 hours to solve them. Scoring will be announced before the round.
We hope you'll like our round...
you were affected, we can make round unrated for you. Please contact
[user:KAN,2017-05-20] with this
Announcement of Codeforces Round 415 (Div. 1)
132.
The Final Round of CROC 2016 and Codeforces Round #347 <br>
Hello Codeforces!
The Final Round of CROC 2016 will be held today at [17:15](http://timeanddate.com/worldclock/fixedtime.html?day=15&month=4&year=2016&hour=17&min=15&sec=0&p1=166) Moscow time, where the best 50 participants from the Elimination Round will be competing for the valueable prices, as well as for their personal entertainment.
Everyone else will be able to participate in Codeforces Round #347 tomorrow at [19:35](http://timeanddate.com/worldclock/fixedtime.html?day=16&month=4&year=2016&hour=19&min=35&sec=0&p1=166) Moscow time that will feature an almost identical problem set.
It is going to be a usual **unrated** round, separate for each division.
The problem set was prepared by Evgeny Vihrov ([user:gen,2016-04-15]), the one and only coordinator of Codeforces Gleb Evstropov ([user:GlebsHP,2016-04-15]) and me.
I would also like to thank Mike Mirzayanov ([user:MikeMirzay...
time that will feature an almost identical problem set. It is going to be a
usual **unrated** round, **UPD 2**: Codeforces Round #347 will be unrated.
Announcement of CROC 2016 - Final Round [Private, For Onsite Finalists Only]
Announcement of Codeforces Round 347 (Div. 1)
Announcement of Codeforces Round 347 (Div. 2)
133.
So many "Fake" newbies in the contest The codeforces round #765 is over, among the top 10 rated users, 5 are newbies, 2 are specialist. Ranking are as below.
If you click on these newbie users, like the 3rd place @Alan_boyfriend, you can see the user previously take part in round 764 and rank 1st. The 8th place, @Asaoix, participated in round 763 and get 6th. And so on....
These newbies, I called, are **fake newbies.** Because they are not newbie level, they are far more than that. Some of the newbie users are even red level, they have low rating only because they are new users and only take a few contest, and the rating cannot accurately measure their level.
Besides, you will not get your performance rating in the contest, if you get rank 1, your new rating will not be rank 1 rating, you new rank will based on your previous rating and this contest performance. If you have 1400 ratin...
cannot make them unrated, it's unfair to them. And here is my suggestion, like
div3 does:
134.
Educational Codeforces Round 27 Hello Codeforces!
On [August 21, 18:05 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?day=21&month=8&year=2017&hour=18&min=5&sec=0&p1=166) Educational Codeforces Round 27 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the [blog post](http://codeforces.com/blog/entry/51208).
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were prepared by Ivan [user:BledDest,2017-08-21] Androsov, Vladimir [user:0n25,2017-08-21] Petrov, Mike [user:MikeMirzayanov,2017-08-02] Mirzayanov and me.
Good luck to all particip...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 27
135.
Codeforces Round 891 (Div. 3) Hello Codeforces!
We are pleased to invite you all to participate in [Codeforces Round 891 (Div. 3)](https://codeforces.com/contests/1857), which will start on [contest_time:1857].
The format of the event will be like any Div. 3 rounds:
- 6-8 tasks;
- ICPC rules with a penalty of 10 minutes for an incorrect submission;
- 12-hour phase of **open hacks** after the end of the round (hacks do not give additional points)
- after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
- by default, only "trusted" participants are shown in the results table.
We encourage participants with a rating of 1600+ not to create new accounts but to participate unofficially.
Only [trusted participants](https://codeforces.com/blog/entry/59228) of the third division will be included in the official standings table. This is a forced measure for combating unsporting behavior. To qualify as a _trusted participant_ o...
is less than 1600 (or you are a newcomer/unrated), then the round will be
rated for you.**
Announcement of Codeforces Round 891 (Div. 3)
136.
Tech Scouts Online Test 2018 (just fun and practice, unofficial, unrated) What do you know about real Mathforces? This is a world full of numbers, theorems and formulas. Are you ready for the adventure full of challenges and dangers in a new world?
Our friends from Harbour.Space University, the International Tournament of Young Mathematicians (ITYM) and St. Paul's International School Barcelona for the second time organize Tech Scouts — two week [International summer camp for high school students](https://codeforces.com/blog/entry/66766). I really think it is a valuable and useful initiative.
For some participants the organizers cover participation fee, the decision is based on the results in special online math test and phone interview.
I invite you to take part in [contest:1164]. It was offered to candidates a year ago, in 2018. This year participants can use it as a practice. I think for many of you it will be interesting to compare your math skills. It starts on [contest_time:1164].
The duration of the test will be 2 hours. You will be ...
Tech Scouts Online Test 2018 (just fun and practice, unofficial, unrated), For sure, the test will be unrated.
137.
Codeforces Beta Round #99 <p>Hello.<br /><br />Today round is prepared by me. My name is Mikhail Tikhomirov, i am fourth grade student at mech.-math. dep. of MSU, also i work as developer-researcher at Yandex.<br /><br />I want to thank Artem Rakhov ([[user:RAD,2011-12-24]]) for valuable help and thoughtful coordination, Maria Belova ([[user:Delinur,2011-12-24]]) for great-as-always translating statements into English, and also[[user:MikeMirzayanov,2011-12-24]] for letting us all get together today. =)</p><p>Round will be for both divisions. Every division will have five problems as usual, some of them will be the same, some will be not.</p><p>Score distribution:</p><p><b>Div1: 500-1000-2000-2000-2500.</b></p><p><b>Div2: 500-1000-1500-2000-3000.<br /></b></p><p>Today round is the last round in 2011. I want to thank Codeforces team, everyone who invented, prepared or helped in preparing problems this or past years, and those, who help developing the project. Codeforces now is not just a platform for programming ...
contest. Out of two unpleasant options: make the round unrated or stay as it
is, we choose the second one
Announcement of Codeforces Beta Round 99 (Div. 1)
Announcement of Codeforces Beta Round 99 (Div. 2)
138.
Educational Codeforces Round 26 Hello Codeforces!
On [August 3, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+26&iso=20170803T1805&p1=166&ah=2) Educational Codeforces Round 26 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the [blog post](http://codeforces.com/blog/entry/51208).
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were prepared by Ivan [user:BledDest,2017-08-02] Androsov, Alexey [user:Perforator,2017-08-02] Ripinen, Mike [user:MikeMirzayanov,2017-08-02] Mirzayanov and me.
Good l...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 26
139.
Educational Codeforces Round 11 Hello, Codeforces!
Educational Codeforces Round 11 will take place on [8 april 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+11&iso=20160408T1500) for the first and the second divisions.
\<The changes in the last paragraph\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.
It seems that it is harder to invent interesting simple problems (like A and B) than difficult ones. So don't be afraid to suggest interesting simple or very simple tasks (of course the difficult tasks are also needed). Please send only the problems for which you know the solution with c...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 11
140.
Educational Codeforces Round 14 Hello, Codeforces!
Educational Codeforces Round 14 will take place on [13 July 2016 at 19:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+14&iso=20160614T1600) for the first and the second divisions.
<I already have a long list of problems, so don't be upset if your problems wasn't used yet>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to me.
It seems that it is harder to invent interesting simple problems (like A and B) than difficult ones. So don't be afraid to suggest interesting simple or very simple tasks (of course the difficult tasks are also needed). Please send onl...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 14
141.
ZOJ Monthly, January 2019 is coming soon! [ZOJ Monthly, January 2019](http://acm.zju.edu.cn/onlinejudge/contestInfo.do?contestId=382) will be held on Saturday [(time)](https://www.timeanddate.com/worldclock/fixedtime.html?month=1&day=19&year=2019&hour=12&min=00&sec=00&p1=33). The main problem setters are [user:chenjb,2019-01-14] and [user:Claris,2019-01-14].
[Contest Link](http://acm.zju.edu.cn/onlinejudge/contestInfo.do?contestId=382)
It will last for 5 hours and have 8-9 problems in total. Since there is no rating system(Thanks to [user:MudCoal,2019-01-14], we may have one in the future) in our [Zhejiang University Online Judge](http://acm.zju.edu.cn/onlinejudge/), it will be unrated. And I guess the difficulty is as a normal Educational Contest in Codeforces.
All problem ideas come from members of Zhejiang University Programming Contest Setting Team and most of them have already been used in the Internal Member-Selection Contests in ZJU held in July, 2018. They have been carefully selected, modified, tested by o...
](http://acm.zju.edu.cn/onlinejudge/), it will be unrated. And I guess the
difficulty is as a normal
142.
Invitation to Mirror BNPC-HS 2022 Final Round <img src="https://raw.githubusercontent.com/ia-toki/toki-assets/master/tlx/contests/bnpc-hs-2022.png" style="width:350px;">
We are excited to invite you to [Mirror BNPC-HS 2022 Final Round (Unrated)](https://tlx.toki.id/contests/bnpchs-2022-final-mirror) on [Sunday, November 6th 2022, 11:05 UTC+7](https://www.timeanddate.com/worldclock/fixedtime.html?msg=BNPC-HS+2022+Final+Round+%28Mirror%2C+Unrated%29+&iso=20221106T1105&p1=3909&ah=5)
The contest will be **5 hours long** and will feature **10 problems**. The order of the problems is the same as the original BNPC-HS contest.
The problems were written by [user:OwenUltima,2022-11-03], [user:vioalbert,2022-11-03], [user:Yoshiyuki,2022-11-03], [user:Kresna,2022-11-03], and [user:alwyn,2022-11-03]
Problem components were prepared by [user:jfcjaya,2022-11-03], [user:OwenUltima,2022-11-03], [user:vioalbert,2022-11-03], [user:rfpermen,2022-11-03], [user:trainerherp,2022-11-03], [user:tyroflex,2022-11-03], [user:Nich728,2022-11-03], ...
We are excited to invite you to [Mirror BNPC-HS 2022 Final Round (Unrated
)](https://tlx.toki.id
143.
Educational Codeforces Round 21 + announcement of 2nd Hello Barcelona ACM-ICPC Bootcamp Hello Codeforces!
On [May 15, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=15&month=5&year=2017&hour=18&min=5&sec=0&p1=166) will be held Educational Codeforces Round 21.
Series of Educational Rounds continue being held as Harbour.Space university initiative! You can read the details about the cooperation between Harbour.Space and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours 30 minutes** to solve them. We hope that everyone will find something interesting in this contest.
The round was prepared by Mikhail [user:PikMike,2017-05-14] Piklyaev, Mikhail [user:MikeMirzayanov,2017-04-14] Mirzayanov and me.
Here is message from Igor Maksimo...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
144.
About cheaters I think this thing bother not only me, but huge part of codeforces community. When I press top button, I expect to see some useful hits, new algos, editorals, invitations to different contests. However, I see 246376243 posts from unrated people who complain about cheating in educational rounds. Personaly, I dont care about this cheating at all. If you get +5, not +6 because of someone cheated its not the end of the world. And cheaters don`t ussualy get first or second place in the contest so they wont be given any material things from sponsors etc. If CP for you is only about rating on website its really bad. For me its a great possibility to practice and solve interesting problems, so cheaters dont interfere me.
I dont know, why so many people try to find cheeaters in every round andhow do they do this, but maybe codeforces should just implement report mechanism? This will release top section from "detectives" and cheaters still will be punished.
I am open to a discussion in c...
. However, I see 246376243 posts from unrated people who complain about
cheating in educational rounds
145.
2018-2019 ACM-ICPC, Asia Shenyang Regional Contest (Online Mirror on Gym) Hi all!
The 2018 ACM-ICPC Asia Shenyang Regional Contest has ended on October 21. At this site, 186 official teams and 6 guest teams selected from the preliminary online contest have competed in **5 hours**, trying to solve **13 problems**.
We are glad to invite you all from Codeforces, one of the greatest programming communities, to participate in its online-mirror contest, [contest:101955]!
Please notice the online-mirror contest will start at an unusual time, [Saturday, November 24, 2018 at 18:00 (UTC+8)](https://www.timeanddate.com/worldclock/fixedtime.html?day=24&month=11&year=2018&hour=18&min=0&sec=0&p1=33), when we are able to answer your questions during the online contest. By the way, we have added the onsite board, so when you are participating (during the mirror contest or virtual participation), you may take advantage of it!
This contest follows [the ACM-ICPC rule](https://icpc.baylor.edu/regionals/rules) and it will be **unrated**. Both personal registration an...
**unrated**. Both personal registration and team registration are recommended.
You may register for
Announcement of 2018-2019 ACM-ICPC, Asia Shenyang Regional Contest
146.
Educational Codeforces Round 32 Hello Codeforces!
On [November 09, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=9&month=11&year=2017&hour=18&min=5&sec=0&p1=166) Educational Codeforces Round 32 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were prepared by Mikhail [user:PikMike,2017-11-08] Piklyaev and me.
Good luck to all participants!
UPD: [Editorial](http://codeforces.com/blog/entry/55701).
I a...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 32
147.
Sorted list of IOI participants by codeforces max rating 1.  [user:matthew99,2017-06-09] 3100
2.  [user:Reyna,2017-06-09] 2771
3.  [user:geniucos,2017-06-09] 2762
4.  [user:yutaka1999,2017-06-09] 2704
5.  [user:jiaqiyang,2017-06-09] 2671
6.  [user:arsijo,2017-06-09] 2638
7.  [user:Enchom,2017-06-09] 2630
8.  [user:Narenji58,2017-06-09] 2613
9.  [user:kefaa,2017-06-09] 2606
10.  [user:pacu,2017-06-09] 2594
11. ![ ]...
172. 
[user:Riodo,2017-06-09]Unrated, ] Unrated
148.
Invitation to CodeChef January Lunchtime 2021 [Replay of Codeflows] We invite you to participate in CodeChef’s [January Lunchtime](https://bit.ly/LTIME92-Codeforces) on 30th January from [9:00 PM to 12:00 AM IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=January+Lunchtime&iso=20210130T21&p1=44&ah=3). **Note the unusual time**.
There will be **3 divisions**, each division containing **6 problems**!
This Lunchtime, [ByteDance](https://en.wikipedia.org/wiki/ByteDance) is joining CodeChef as the official contest recruiter! The tech giants, who have their presence globally established through a range of content platforms, are looking to hire for multiple positions for their Singapore office, including — Algorithm Engineers, Backend Engineers, Data Engineers, Data Scientist, Machine Learning Engineers, Research Scientists, Frontend Engineers, Quality Assurance Engineer, Research Engineers, Software Engineer, and Site Reliability Engineers.
Joining us on the problem setting panel are:
- Admins: Ashish [user:ashishgup,2020-12-...
The January Lunchtime is being made **unrated** due to the various issues that
users faced.
149.
Educational Codeforces Round 5 Hi, Codeforces!
Happy New Year! Holidays and 2015 year have passed and year 2016 is ahead. I wish you good luck in programming competitions and achieving all of your goals this year.
<img src="http://www.keviniriarte.com/wp-content/uploads/2014/04/new_season.jpg" style="max-width:100%; max-height:100%"/>
Educational Codeforces Round 5 will take place on [11 January 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+5&iso=20160111T1500) for the first and second divisions. You can read about educational rounds [here](http://codeforces.com/blog/entry/21496) and [here](http://codeforces.com/blog/entry/21565).
\<A year has passed, but paragraph remains unchanged.\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 5
150.
Solutions for April Fools Day Contest 2023 in one line (Collection) Hi, I collected the solutions for the problems of April Fools Day Contest 2023. Before the official editorial being posted, we can discuss about the problems here.
P/s: The editorial was published.
[problem:1812A]
<spoiler summary="Solution">
I tried to submit `NO`, but what we all need is to submit `security`
</spoiler>
[problem:1812B]
<spoiler summary="Solution">
It's about the first $25$ contest ever, the $15^{th}$, $20^{th}$ and $21^{th}$ one was unrated.
</spoiler>
[problem:1812C]
<spoiler summary="Solution">
The first test case has $3$ numbers, the second has $1$, and the third has $4$. Yes, they are following the order of number pi.
`314159265358979323846264338327950288419716939937510582097494459230781640628620899862803482534211706798214808651328230664709384460955058223172535940812848111745`
Take this string into your code and you will be fine. Multiply all number in a test and get the answer.
</spoiler>
[problem:1812D]
<spoiler summary="So...
$21^{th}$ one was unrated.
151.
Educational Codeforces Round 28 Hello Codeforces!
On [September 05, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=5&month=9&year=2017&hour=18&min=5&sec=0&p1=166) Educational Codeforces Round 28 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 problems** and **2 hours** to solve them.
The problems were prepared by Mikhail [user:PikMike,2017-09-04] Piklyaev, Vladimir [user:0n25,2017-09-04] Petrov and me.
Good luck to all participants!
UPD. Editorial can be fo...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 28
152.
Educational Codeforces Round 10 Hello, Codeforces!
[Note the unusual (for the educational round) start time!]
Educational Codeforces Round 10 will take place after a long delay on [25 march 2016 at 16:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+10&iso=20160325T1300) for the first and the second divisions. The long delay is caused by the high frequency of contests and championships on Codeforces. You can read about educational rounds [here](http://codeforces.com/blog/entry/21496) and [here](http://codeforces.com/blog/entry/21565).
\<The same as before\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prepared problems that you can't use in rounds or official competitions, you can write to m...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 10
153.
Educational Codeforces Round 9 Hello, Codeforces!
Today is the first day of the spring and it's great!
<img src="http://codeforces.com/predownloaded/eb/28/eb283da2b55682fbdfeebdb3823ad94cbe76ac4a.jpg" style="max-width:100%; max-height:100%"/>
Educational Codeforces Round 9 will take place on [01 march 2016 at 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+9&iso=20160301T1500) for the first and the second divisions. You can read about educational rounds [here](http://codeforces.com/blog/entry/21496) and [here](http://codeforces.com/blog/entry/21565). I should again notice the high density of contests and championships.
\<This time it wasn't changed\>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or ma...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
154.
SPC — Final Contest : ) Hola, budding coders of the SPC and Codeforces!
On [contest_time:338837], [Programming Club IIT Madras](http://cfi.iitm.ac.in/club/Programming%20Club) will host The [Speed Programming Contest (SPC) — Final Contest](https://codeforces.com/contestInvitation/ddb5bcb7cacfa3a53bb1e9e92f99927d51a6c095) and we would like to invite all of you for the same.
This is the Last round of the 2021 series of Summer Programming Camp Contests. It will be a combined **unrated** round for all divisions : )
The contest consists of 12 problems [ICPC Style Scoring] to be solved in 150 minutes. While all the problems will be exciting and fun for the participants of the Camp, we believe that the first 4 problems would be easy for the experienced coders & the later problems would be challenging even for a Master.
The round will provide a good range of problems in terms of difficulty, and every problem would definitely be thrilling for the Participants.
The prizes for the **Official Particip...
combined **unrated** round for all divisions : )
155.
Community Solutions to Abuse of Rules Hi!
Codeforces is filled with great people, but it is also has plenty of users that abuse the system, and dampen other people's fun though their actions. A few problems I put under the spotlight
Problems:
------------------
<span style="color:red"><b>A</span> unrateds, alts, and rating-manipulating contestants that win contests below their division, stealing the victory and some rating from legitimate participants. See the last 4-5 div 2's for sufficient examples of experts and specialists losing wins to these fakes. This can be extended to cheaters in general, but there is already a system for that in place.
<span style="color:blue"><b>B</b></span> Users who make alts to shield themselves from backlash when commenting, potentially to make hurtful statements. Many of us have seen the abuse that they spew.
I've labeleld things as <span style="color:red"><b>A</span> and <span style="color:blue"><b>B</b></span> to refer to the problem I am talking about.
I've done my rese...
156.
Educational Codeforces Round 13 Hello, Codeforces!
Educational Codeforces Round 13 will take place on [13 June 2016 at 19:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+13&iso=20160613T1600) for the first and the second divisions. Almost two months passed from the previous round. That is due the next reasons: 1) I coordinated regular CF-round at the end of April; 2) about whole CP community were busy with preparing and competing in ACM ICPC WF in May; 3) at the beginning of this month I start to work at AimTech (I hope that I'll have enough time to continue prepare ERs).
<It's need to read at least once maybe you'll find something interesting>
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve six problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
If you have ideas for some problems or maybe already prep...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 13
157.
Codeforces Round #730 (Div. 2) Hello Codeforces!
I am quite excited to invite you to my first ever round, [contest:1543] which will start on [contest_time:1543]. **The round will be rated for participants of Division 2 (having rating strictly less than 2100).** As always, Division 1 participants are welcome to participate in the round but it will be unrated for them.
The problems of this round will be themed on the 2005 video game <B><I>Need For Speed: Most Wanted</I></B>. You will be given **5 problems** and **2 hours 15 minutes** to solve them. One of the problems will be **interactive**. So, it is recommended to read the [guide on interactive problems](https://codeforces.com/blog/entry/45307) before the round.
I would like to thank -
- [user:Aleks5d,2021-07-05] for coordinating the round and not rejecting any of my problems :)
- [user:KAN,2021-07-05] for reviewing all the problems and providing invaluable suggestions throughout the round preparation.
- [user:mshiladityam,2021-07-05] and [user:ya...
be unrated for them.
Announcement of Codeforces Round 730 (Div. 2)
158.
VK Cup 2018 — Wild-card Round 1 Hi!
Tomorrow, on [March 17th, 2018, at 15:35 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?msg=VK+Cup+Wild-card+Round+1&iso=20180317T1835&p1=166&ah=2) the first Wild-card Round of VK Cup 2018 will be held. Along with it we will host a parallel unofficial round in which everyone can take part.
The rounds will use **special rules, the rounds will be unrated.** The problems were prepared by Codeforces team: [user:fcspartakm,2018-03-16], [user:MikeMirzayanov,2018-03-16] and me. Thanks to [user:Vovuh,2018-03-16], [user:GreenGrape,2018-03-16], [user:neckbosov,2018-03-16], [user:glebodin,2018-03-16] and [user:gritukan,2018-03-16] for testing the round and their help to make the round better!
The detailed rules will be added to this post around 30 minutes before the start. There will be 24-hours open hacks phase after the round, like in Codeforces Educational Rounds.
**Round rules:**
The round will be almost usual contest with ACM ICPC rules. There will be 10 proble...
The rounds will use **special rules, the rounds will be unrated.** The problems
were prepared by
Announcement of VK Cup 2018 - Wild-card Round 1
Announcement of VK Cup 2018 - Wild-card Round 1 (unofficial unrated mirror)
159.
solved.ac Grand Arena #1 Announcement Hi, I am [user:TheQueenOfHatred,2023-08-02], staff of the Korean programming site -- [solved.ac](https://solved.ac/en).
We will hold solved.ac Grand Arena Round 1.
- **Time**: https://www.timeanddate.com/worldclock/fixedtime.html?iso=20230806T14&p1=235&ah=3, 180 minutes
- **Problems**: 9, in ICPC format
- **Difficulty**: **Problems A and B are the first and second easiest problems expected by the jury.** The order will be random except for problems A and B. All problems' difficulty will be between Bronze and Diamond by the solved.ac scale.
- **Penalty**: 20 minutes; The scoreboard will freeze 30 minutes before the contest ends. Compilation errors do not count toward penalties.
- **Scoreboard**: ICPC style. The contestant with more solves is ranked in a higher place. If two contestants have the same number of solves, the contestant with the small amount of the sum of penalties over all accepted problems is ranked in a higher place.
- **Time and memory**: There is a handicap f...
memory**: There is a handicap for some languages. - **Rated range**: Unrated —
SS+.
160.
Typescript SDK for codeforces ## Hello codeforces!
You know you are a programming competitions addict when [this blog](https://codeforces.com/blog/entry/12968) was 9 years ago, but you thought it was no more than 3...
More than month ago or, to be more precise from 15 to 19 December 2022, codeforces has five contests in five days. I participated in all of these contests and I thought how many contestants took part in all 5 contests?
**TLDR**: If you don't want to read why I decided to implement SDK on typescript and how I struggled with python, just scroll down to Typescript paragraph.
**TLDR2**: Links are below.
## Python
Historically I have some python scripts to work with codeforces API, so I've created `allContests.py` file, imported my old library code with method `cf` and paused for a while. Which arguments does this method have? Let's look into source code. Ah, clear, `def cf(method, **kwargs)`.
F**k. OK, let's go to [API](https://codeforces.com/apiHelp/methods#contest.standings) page. O...
Why? Because unrated users don't have rating, they have `undefined` instead. If
you are sure, that
161.
Unfair Plagiarism Allegation: My Experience in Codeforces Round 937 (Div. 4) **Hi Codeforces !**
Six days ago, I eagerly participated in **Codeforces Round 937 (Div. 4)**, pouring hours of effort into crafting original solutions to the challenging problems presented. Today, to my dismay, I discovered that all my submissions were flagged for **plagiarism.**
Upon thorough investigation, I found that my code had been marked as plagiarized due to similarities with several other submissions. However, **I want to emphasize that I did not resort to any online compiler nor did I copy code from any external source.**
#### **These are some points that I want to put forth which I think the readers should know :**
- **The code to find the factors of a number is easily available online** _(I didn't use it though as I have appeared in 80+ contest and the idea of finding factors is quite common)_ [Link](https://www.geeksforgeeks.org/find-all-factors-of-a-natural-number/)
- The other solutions use a **triple nested loop**, to check for the similarities of substri...
- I am a specialist (1479) and div 4 contests are unrated for me, so why would
I risk plagiarism in
162.
Short Editorial of SRM 651 Div1 Hello, I'm the writer of SRM 651.
It turns out this round is unrated due to some system failure. Sorry about the inconvenience it caused. I hope Topcoder can improve their infrastructure soon so that can be as good as codeforces.
I will post the problem statement, reference solution and a short editorial here.
Welcome to discuss the tasks, as well as to give feedback about them!
**Problem Statement**: [http://www.speedyshare.com/2kRaC/task.rar](http://www.speedyshare.com/2kRaC/task.rar)
**Reference solution**:
Div1-Easy: [http://ideone.com/a9siv1](http://ideone.com/a9siv1)
Div1-Medium: [http://ideone.com/sbEZSH](http://ideone.com/sbEZSH)
Div1-Hard: [http://ideone.com/9JXoSL](http://ideone.com/9JXoSL)
**Div1-Easy: RobotOnMoon**
Look at this example:
~~~~~
....
.S.#
....
~~~~~
There will be infinite long perfect safe sequence, why? because we have "RRR...".
That means if there is one '#' at any of the 4 direction of 'S', then the answer w...
It turns out this round is unrated due to some system failure. Sorry about the
inconvenience it
163.
Data Structures in Dynamic Programming Week [](https://youtu.be/Aaceu-Z0abc)
(click on the thumbnail to watch a YouTube video)
Welcome back to what I called "ds in dp week", and you'll see in a second what this is all about. But first I wanted to share some stats with you:
### Contests
This week I took part in 7 contests. Four of them are rated for me, and in the remaining three, I participated unofficially.
I took second place in the Hacker Earth's Easy competition, got on the first standings page of LeetCode Biweekly Contest 69, and had my best TopCoder performance so far, which saw 164 points rating increase.
Codeforces' Hello 2022 didn't go so well, with me managing to solve only A-D. Luckily I only got -15, a surprisingly forgiving rating change for an underperformance.
The remaining three competitions were unrated for me, so I didn't pay much attention to them. It partially explains my questionable results on CodeChef Start...
The remaining three competitions were unrated for me, so I didn't pay much
attention to them. It
164.
April Fools Day Contest 2016 The contest is over; I hope you've enjoyed it :-) Editorial is [here](http://codeforces.com/blog/entry/44141). See you next year!
---
The fourth April Fools Day Contest will take place on Friday April 1st. This is a joke competition in which solving the problem is often easier than figuring out what the actual task is. Thanks to [user:kit1980,2016-03-31] and Codeforces team for their help in preparing problems.
In this round you'll be given 7 weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces — well, unless the problem says otherwise ;-) To get an idea of what the contest will look like, you can check out the contests of the past years: [2012](http://codeforces.com/contest/171), [2013](http://codeforces.com/contest/290), [2014](http://codeforces.com/contest...
earned on them), and it will be unrated. You can submit solutions in any
language allowed by
Announcement of April Fools Day Contest 2016
165.
Invitation to Code Venture Hello Codeforces!
We are glad to invite you to participate in a contest hosted by technical fest **Pragyan, NIT Trichy**, which will take place on **Thursday, 23rd March, from 5:30 PM to 7.10PM IST.**
<br />
<br />
<br />
<center>
</center>
<br />
<br />
**Pragyan**, in association with **Spider**, presents **Code Venture**. An competitive programming contest on Codechef which will go live on 23rd March from 5:30-7:10 pm. An 100 minute contest to test your problem solving and thinking abilities.
Think you have what it takes to reach the top? Test your programming skills in a **beginner friendly contest**.
The contest is unrated for everybody and common for all divisions.
**CASH PRIZES Distribution** (Indian Participants):
- Top 3 performers will be awarded cash prizes of INR 15000, 9000, and 6000, respectively.
**Contest Link:** [CDVN23](htt...
The contest is unrated for everybody and common for all divisions.
166.
About the issue of Educational Codeforces Round 73 First of all, I'm really sorry for the issues the round had. We paid not enough attention to make sure everything works as intented and got punished for it. That was a lesson for us, we'll do our best to keep the future rounds as clean as possible.
The problem B had an issue with the checker, solutions have been recieving wrong verdicts. Unfortunately, neither its author, nor reviewers have noticed the bug.
Can you spot it without looking in comments?
<spoiler summary="The bugged checker">
``````
#include <bits/stdc++.h>
#include "testlib.h"
#define forn(i, n) for (int i = 0; i < int(n); ++i)
using namespace std;
int n;
string w[143];
int dx[] = {-2, -2, -1, -1, 1, 1, 2, 2};
int dy[] = {-1, 1, -2, 2, -2, 2, -1, 1};
bool good(int x, int y)
{
return (x >= 0 && x < n && y >= 0 && y < n);
}
int readAndCheckAnswer(InStream& in) {
for(int i = 0; i < n; i++)
w[i] = in.readLine(format("[BW]{%d}", n).c_str(), "s");
int ans = 0;
for(int i = 0; i < n;...
The contest will definitely be unrated for the participants affected by it.
167.
AtCoder Beginner Contest 164 Announcement We will hold AtCoder Beginner Contest 164.
- Contest URL: https://atcoder.jp/contests/abc164
- Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20200426T2100&p1=248
- Duration: TBD (around 2 hours)
- Number of Tasks: 6
- Writer: kyopro_friends, [user:Kmcode,2020-04-25], [user:latte0119,2020-04-25], [user:smeke,2020-04-25], ynymxiaolongbao, wo01
- Rated range: ~ 1999
The point values will be 100-200-300-400-500-600.
We are looking forward to your participation!
Addition: About the Unrated ABC163
We are sorry for the inconvenience.
The server down during the last contest was caused by a sudden access to the ALB, and we found that we could solve this problem by doing Pre-Warming.
Also, the bug where the problem statement does not show up has been resolved by changing the caching algorithm.
The problem with submissions showing up as IE (Internal Error) was due to the Judge server's scoring algorithm being different than in the past. This too h...
Addition: About the Unrated ABC163
168.
A Recap of My First Year in CodeForces Hello all on Codeforces!
------------------
It’s been just over a full year since I created my Codeforces account. Since then a lot has happened on my Codeforces journey so far. With everything that’s happened I want to look back at how I got to my current point, share what I learned in the process, recap some of my best moments, and laugh at whatever I was thinking on a few of these contests, because a lot happened. The only issue is that there’s no way I’m going to detail all **60** contests I took part in 2022. Instead I’ve chosen to “award” the 9 most memorable contests, wheter it be because I did exceedingly well or self destructed in almost hilarious fashion.
A few notes before I begin: No full solutions for any problems are shown in this post but there are code snippets and discussions that are spoilers for these problems. I apologize in advance.
### First Contest — [Hello 2022](https://codeforces.com/contest/1621)
This was the first contest held in 2022, ...
unrated.
169.
Codeforces Marathon Round 2 Hi all!
I invite you to take part in Codeforces Marathon Round 2.
The contest will start on Tuesday, [July 24, 2018 at 15:00 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Codeforces+Marathon+Round+2&iso=20180724T15&p1=3905), and will last for 7 days.
There will be one problem based on game mechanics of a couple of board games for children.
The problem most likely does not have a fast and full solution.
So the solutions will be given scores, and the winner will be the one who gets the highest total score.
The contest will be unrated because the problem is considerably different from the problems of rated rounds.
During the time of the contest, the solutions will be checked on examples and preliminary tests.
After the contest is over, the final solution of each contestant will be checked on the final test set, and the total score for this test set will determine the final scoreboard.
The contest will take place on Codeforces platform and is supported by th...
The contest will be unrated because the problem is considerably different from
the problems of
Announcement of Codeforces Marathon Round 2
170.
Microsoft Q# Coding Contest — Summer 2020: Main round Microsoft's Quantum team and Codeforces are excited to invite you to Microsoft Q# Coding Contest — Summer 2020!
The contest will run from **June 19 to June 22**.
As a reminder, last weekend we held a warmup round with easier tasks on the topics that have not been covered in the [previous contests](https://codeforces.com/contests/1116,1115,1002,1001). You can find the problems from the warmup round for practice [here](https://codeforces.com/contest/1356), and the described solutions [here](https://codeforces.com/blog/entry/78832). There is also a list of great learning and practice resources [here](https://codeforces.com/blog/entry/77614).
Several useful reminders:
* The contest is unrated :-)
* Solutions are accepted only in Q#.
* The tasks are grouped by topic, and the tasks within one topic are ordered in approximate order of increasing difficulty. If you find a problem too hard, check the next problems in this topic and problems from different topics, they might tu...
* The contest is unrated :-) * Solutions are accepted only in Q#. * The tasks
are grouped by
Announcement of Microsoft Q# Coding Contest - Summer 2020
171.
solved.ac Grand Arena #3 Announcement Hi, I am [user:TheQueenOfHatred,2023-11-12], staff of [solved.ac](https://solved.ac/en). It's been a while!
We will hold solved.ac Grand Arena Round 3. ([Division 1](https://www.acmicpc.net/contest/view/1197) / [Division 2](https://www.acmicpc.net/contest/view/1198))
- **Time**: https://www.timeanddate.com/worldclock/fixedtime.html?iso=20231126T14&p1=235&ah=3, 180 minutes
- **Problems**:
- **Division 1**: 7-8, in ICPC format
- **Division 2**: 7-8, in ICPC format
- **Difficulty**:
- **Division 1**: **Problems A and B are the first and second easiest problems expected by the jury.** The order will be random except for problems A and B.
- **Division 2:** Problems are sorted ascending by the difficulty expected by the jury.
- **Penalty**: 20 minutes; The scoreboard will freeze 30 minutes before the contest ends. Compilation errors do not count toward penalties.
- **Scoreboard**: ICPC style. The contestant with more solves is ranked in a higher place. If two c...
:** Everyone. (Unrated — X) - **Division 2:** Unrated — S+. - For participants
in
172.
Codeforces Upsolving Helper <spoiler summary="UPD(July 24, 2020)">**Randomize Button** added at the end of each section in **All Problemset Recommender** .
</spoiler>
<spoiler summary="UPD(July 19, 2020)">
**Unattempted Problem Recommender** from **Past Contests** (as suggested by [user:sharatsachin,2020-07-20] and [user:mr_robot11,2020-07-20]) and from **All Problemset** (as suggested by [user:ekaerovets,2020-07-23]) has been introduced .
</spoiler>
<spoiler summary="UPD(July 14, 2020)">
**Team Mode** has been introduced as suggested by [user:socho,2020-07-13].
</spoiler>
<spoiler summary="UPD(July 11, 2020)">
Rated and Unrated Problems are now separated under respective headings in each section(when Problems are segregated by Index) as suggested by [user:gol_en_05,2020-07-12] .
 Hello, Codeforces!
The 2018 ICPC Asia-East Continent Final has ended on last Sunday. At this site, over $380$ teams have competed in **5 hours**, trying to solve **12 problems**.
The problems are prepared by [user:CommonAnts,2018-12-18], [user:Claris,2018-12-18] and me. Thanks to [user:skywalkert,2018-12-18], [user:quailty,2018-12-18], [user:zscc,2018-12-18], [user:yefllower,2018-12-18],[user:niike0goood,2018-12-18], [user:AHdoc,2018-12-18], [user:C_SUNSHINE,2018-12-18] for discussing and testing the problems, [user:whzzt,2018-12-18], [user:yjq_naiive,2018-12-18], [user:fjzzq2002,2018-12-18] for their amazing performance in the test contest.
Moreover, special thanks to [user:CommonAnts,2018-12-18], [user:skywalkert,2018-12-18], [user:C_SUNSHINE,2018-12-18], [user:Claris,2018-12-18], [user:niike0goood,2018-12-18] for preparing the statement. To ensure the correctness of the statement, they updated it for over **180** times before the conetst. Thanks a lot for their efforts.
...
**unrated**.
Announcement of 2018-2019 ACM-ICPC, Asia East Continent Finals
174.
Codeforces Round #655 Editorial We really hope you enjoyed the problems! We apologize again for the long queue and unrated round. Just for fun, here's how many of our problems were rejected:
<spoiler summary="Rejection Count">
2A: 12
2B: 16
2C: 5
2D: 19
2E: 18
2F: 2
Total: 72
</spoiler>
[tutorial: 1372A]
Solution: [submission:86603804]
Idea: [user:MagentaCobra,2020-07-11]
Preparation: [user:MagentaCobra,2020-07-11], [user:qlf9,2020-07-11]
[tutorial: 1372B]
Solution: [submission:86603838]
Idea: [user:qlf9,2020-07-11]
Preparation: [user:qlf9,2020-07-11]
[tutorial: 1372C]
Solution: [submission:86603857]
Idea: [user:MagentaCobra,2020-07-11]
Preparation: [user:MagentaCobra,2020-07-11], [user:qlf9,2020-07-11]
[tutorial: 1372D]
Solution: [submission:86603878]
Idea: [user:MagentaCobra,2020-07-11]
Preparation: [user:MagentaCobra,2020-07-11], [user:Tlatoani,2020-07-11]
[tutorial: 1372E]
Solution: [submission:86603896]
Idea: [user:golions,2020-07-11]
Preparation: ...
We really hope you enjoyed the problems! We apologize again for the long queue
andunrated round
Tutorial of Codeforces Round 655 (Div. 2)
175.
Invitation to IndiaHacks 2nd Elimination 2017 On [Sunday, August 6th, 22:00 IST](https://www.timeanddate.com/worldclock/fixedtime.html?iso=20170806T22&p1=438&ah=3), we will hold the 2nd elimination for IndiaHacks (some more details [here](http://codeforces.com/blog/entry/52069)). The top 900 individuals who qualified through previous rounds will have the opportunity to participate in this round. The top 25 global participants and top 25 Indian participants will advance to the final round. The link to the contest is [here](https://www.hackerearth.com/challenge/competitive/indiahacks-2017-programming-wave-20-eliminator/).
After the official round is over, the next morning, on [Monday, August 7th, 11:35 IST](https://www.timeanddate.com/worldclock/fixedtime.html?day=7&month=8&year=2017&hour=9&min=5&sec=0&p1=166), we'll hold an unofficial unrated mirror here on Codeforces. This mirror will have ICPC rules. For participants of the official round, please hold off on discussing the problems publicly until after this mirror is over.
...
hold an unofficial unrated mirror here on Codeforces. This mirror will have
ICPC rules. For
176.
CROC 2016 — Elimination Hey Codeforces!
The Elimination Round of the CROC 2016 Championship will take place on [Friday, March 18 at 16:35 UTC](http://www.timeanddate.com/worldclock/fixedtime.html?day=18&month=3&year=2016&hour=19&min=35&sec=0&p1=166). After [our last round](http://codeforces.com/blog/entry/21860), Yang Liu ([user:desert97,2016-03-17]), Michael Kural ([user:pi37,2016-03-17]) and I realized that we haven't had enough, so we joined forces with Kevin Sun ([user:ksun48,2016-03-17]) and Daniel Chiu ([user:waterfalls,2016-03-17]) to prepare another problem set for you guys. Our contest will be for combined divisions and consist of seven problems. And although only those who pass the Qualification Round can participate officially, the round will be open to and rated for all Codeforces users. As always, we'll be taking the tractor to Bovinia for some <s>farmland</s> algorithmic adventures with Farmer John, Bessie and her best friend Elsie!
Before we begin, we'd like to thank [user:GlebsHP,2016-03...
place, please write [user:MikeMirzayanov,2016-03-19] to make your participation
unrated. Sorry about
Announcement of CROC 2016 - Elimination Round
Announcement of CROC 2016 - Elimination Round (Rated Unofficial Edition)
177.
How to train: why it's not enough to just do a lot of tasks Hello, Codeforces! I, like many of you, read blogs periodically. Lately, blogs from low-rated users who ask me how to raise their ratings have been catching my attention. I want to tell you a little bit about my opinion on these blogs.
So what do these blogs look like? Usually this is a blog with a title something like <b>"I need help right now!"</b> or <b>"How to improve my rating, help me!"</b> When you open this blog, you see the most detailed description of the problem, such as: "I have solved 500 problems, but no improvement" or "I have solved 100 problems with rating >= 1500, but my rating is not increasing". And in the comments they usually write "you haven't solved enough, solve more" or "solve more difficult problems". <b>In my opinion, this is incorrect and misleads such users.
So, imagine that you do not know anything at all about sports programming, or even about the basics of Olympic math. You at best (because many people don't even do that) have learned a programmin...
, perhaps unrated, practice rounds. I understand that a lot of effort is put
into each Codeforces round by
178.
Codeforces Round #296 Hi everybody! There will be a Codeforces Round for both divisions today at [standard time](http://timeanddate.com/worldclock/fixedtime.html?day=17&month=3&year=2015&hour=19&min=30&sec=0&p1=166) set up by me.
My teammates from ICPC team Moscow SU Trinity [user:sankear,2015-03-17] and [user:malcolm,2015-03-17] helped me a lot while preparing this round, also there were lots of useful tips and advices from [user:MikeMirzayanov,2015-03-17], applause for them. English translation was made by our veteran translator [user:delinur,2015-03-17].
As usual, there will be five tasks for two hours. The scoring will be announced later.
See you on the round! I hope that each contestant will be able to find something nice in ongoing problems.
**UPD**: Scoring is standard.
**UPD2**: Due to technical issues the round is delayed by 15 minutes. We are sorry for an inconvenience.
**UPD3**: We are sorry for an inconvenience with the task Div1-D. The pretest #16 wasn't satisfying the constra...
unrated for you.
Announcement of Codeforces Round 296 (Div. 2)
Statements of Codeforces Round 296 (Div. 1)
179.
Kotlin Heroes 6 Announcement <img src="/predownloaded/6b/62/6b62332b37519ade4a4d42cb266937c422b64557.png" style="width:500px;float:right;margin:0 1em 1em 1em;"/>
Hello, Codeforces!
First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the five Kotlin Heroes competitions which were held previously: [Episode 1](https://codeforces.com/contests/1170), [Episode 2](https://codeforces.com/contests/1211), [Episode 3](https://codeforces.com/contests/1297), [Episode 4](https://codeforces.com/contests/1346), and [Episode 5: ICPC Round](https://codeforces.com/contest/1431).
Ready to challenge yourself to do better? The [contest:1488] competition will be hosted on the Codeforces platform on [contest_time:1488]. The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard ones, to make it interesting for seasoned competitive programmers.
**Prizes:**
**Top three winners will ge...
- The round is unrated. - The contest will have 9 problems of various levels of
complexity. - You
Announcement of Kotlin Heroes: Episode 6
Announcement of Kotlin Heroes: Practice 6
180.
Tutorial and tips to reach Master. "As mentioned earlier, practice hard. This is the only common factor that experts have. And for whom reached expert, I'll write a sequel from expert to master soon." (From my blog, Tutorial and tips to reach Expert). That soon happened to be 1.5 years after the first blog......
First, I'm sorry for the immense delay. Many bad things happened to me, like not staying in the Master rating range, having a health problem, etc. That's why I wrote the blog this late.
Introduction
------------------
This is a sequel, but I am going to write the steps to Expert from scratch since the original blog([https://codeforces.com/blog/entry/81882](https://codeforces.com/blog/entry/81882)) has poor quality.
Your journey is going to be divided into 4 sections. Each section contains the knowledge you need to have, the practice you must do, the performance you need to have in a contest, etc to advance to the specific rating.
Section 1. From the beginning to escaping Gray(1200)
---------------...
becomes unrated after you get to the orange. Therefore, you have two ways., trend continues for all cyans except unrated(1500)s.
181.
The 75 Hard coding challenge! Hi Coders!
I hope everyone of you is doing great! A member of my Discord server [user:BadalArya,2023-09-13] recently came up with an idea to conduct a 75 Hard challenge (similar to the fitness one) for coding. I am excited to announce that we have concluded the development of the bot and have integrated it to our discord server to help coders track their progress for this challenge.
This is how the challenge looks:
1. The bot provides 2 problems daily to each user (who ask for the challenge using the command ";hard75 letsgo"). These problems are based on the users cf rating (one problem is of the same rating and other is of +200 level NOTE: both these ratings are rounded to nearest 100).
2. On completion the user has to instruct the bot to check the progress using the command ";hard75 completed", the bot then checks whether user has completed both the problems on codeforces and accordingly saves his progress and the streak.
3. On completion of 75 days the bot would acknowledge t...
**UPDATE 2 (Week 1 concludes)**: The contestant rating varies from 3064 (LGM)
to 0 (unrated). **375
182.
ICPC WF Moscow Invitational Contest — Online Mirror Hello, everybody!
We would like to invite you to participate in the Mirror of The ICPC World Finals Moscow Invitational Contest. The original contest was made for the teams who cannot come to The World Finals in Moscow. They were competing for the medals and glory. The Invitational contest has already passed and the results will be revealed on October 5th.
The mirror contest will be held by almost standard ICPC rules with 10 to 14 problems. The difference from the traditional ICPC format is that your team can use three computers instead of one. The problems are expected to be of The World Finals difficulty. **Also, the round will be unrated!**
The problemset was prepared by NERC Jury Team with the help of many other people. The chief judge is Roman [user:elizarov,2021-09-30] Elizarov. The jury members are Pavel [user:PavelKunyavskiy,2021-09-30] Kunyavskiy, Georgy [user:kgeorgiy,2021-09-30] Korneev, Evgeny [user:eatmore,2021-09-30] Kapun, Ilya [user:izban,2021-09-30] Zban, Niya...
problems are expected to be of The World Finals difficulty. **Also, the round
will beunrated!**
183.
Pinely Treasure Hunt Contest Hello, codeforces!
Pinely is a high-frequency trading company. We trade at the exchanges all over the world. This year we are the sponsors of the online PTZ competitive programming camp. We have prepared a fun contest for camp participants and invite everybody to join it on CodeForces!
[Pinely Treasure Hunt Contest](https://codeforces.com/contests/1639) will be held on Saturday, [contest_time:1639].
The participants will be offered to solve an interactive optimization problem with open tests and will have 3.5 hours to work on it. You can join individually or in teams of up to 3 people. The contest will be **unrated**.
Winners among camp participants as well as the 3 best teams in overall standings will be awarded with pinely t-shirts.
Since the contest is targeted for participants of the PTZ training camp, it'll be most interesting for **participants with codeforces rating 2000+**.
We are grateful to [user:MikeMirzayanov,2022-02-03] for the opportunity to host the conte...
contest will be **unrated**. Winners among camp participants as well as the 3
best teams in overall
Announcement of Pinely Treasure Hunt Contest
184.
[Bug] Invalid testcase(s) for Problem-B from 2022-2023 ICPC, NERC, (Unrated, Online Mirror) I recently encountered [Problem-B BinCoin](https://codeforces.com/contest/1773/problem/B) from **2022-2023 ICPC, NERC, Northern Eurasia Onsite (Unrated, Online Mirror, ICPC Rules, Teams Preferred)** while practicing random 2200 problems. <br>
The problem is based on a binary rooted tree generated by the jury, and a random in-order traversal of that tree.
I was sure my solution to this problem was reliable. But it seemed to RTE on test-16 (Which in these rounds is not visible). I tried several methods to circumvent the situation to no avail.
<spoiler summary="My Approach">
Let $a$, $b$ and $c$ be some $3$ employees then <br>
$bac$ or $cab$ is reliably a sub-array (at least any one of them at a time) in each journal if and only if $b$ and $c$ be leaf nodes and have a common parent $a$.
And there will always be at-least $1$ such triplet.
<spoiler summary="Proof of the 'if and only if' part">
For $bac$ or $cab$ to be a sub-array, it is necessary that at-least one of $b$ or $...
[Bug] Invalid testcase(s) for Problem-B from 2022-2023 ICPC, NERC, (Unrated,
Online Mirror), **2022-2023 ICPC, NERC, Northern Eurasia Onsite (Unrated, Online Mirror, ICPC
Rules, Teams Preferred
185.
Educational Codeforces Round 146 [Rated for Div. 2] Hello Codeforces!
On [contest_time:1814] [contest:1814] will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://mirror.codeforces.com/blog/entry/51208">blog post</a>.
This round will be **rated for the participants with rating lower than 2100**. It will be held on extended ICPC rules. The penalty for each incorrect submission until the submission with a full solution is 10 minutes. After the end of the contest, you will have 12 hours to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **6 or 7 problems** and **2 hours** to solve them.
The problems were invented and prepared by Adilbek [user:adedalic,2023-04-05] Dalabaev, Ivan [user:BledDest,2023-04-05] Androsov, Maksim [user:Neon,2023-04-05] Mesche...
**UPD: The contest is unrated. We apologize for the inconvenience.**
Announcement of Educational Codeforces Round 146 (Rated for Div. 2)
186.
Invitation to CodeChef May Lunchtime 2019 sponsored by ShareChat! Greetings Codeforces community!
CodeChef’s May Lunchtime sponsored by ShareChat is just around the corner and you are all invited to participate. This is not only an opportunity to get some practice and improve your coding skills, but also a chance to improve your rating!
Team CodeChef is also seeking problem ideas for our upcoming contests! If you think you have an idea that will make for an exciting contest problem, then send it to us using this form: https://www.codechef.com/problemsetting/new-ideas. Come and take your first step towards becoming a CodeChef problem setter!
ShareChat — India’s fastest growing social network is inviting participants of the Lunchtime to come apply for exciting work opportunities. Job opportunities are open to programmers across the world and internship opportunities are exclusively aimed at final year B.Tech students who have already been placed and looking forward to gaining startup experience. Visit the contest page for more details.
...
**UPD:** Unfortunately the contest is going to be unrated due to server issues.
187.
Codeforces Round #637 — Thanks, Ivan Belonogov! Hello, Codeforces!
I'm glad to invite you to [contest:1340] and [contest:1341], which will be held on [contest_time:1340]. The round will be rated for both divisions (I hope).
All problems were written and prepared by Aleksey [user:Aleks5d,2020-04-22] Upirvitskiy, Alexey [user:alexX512,2020-04-22] Perevyshin and by me, Denis [user:i_love_myself,2020-04-22] Sapozhnikov. Thanks to [user:300iq,2020-04-22], [user:voidmax,2020-04-22], [user:ashmelev,2020-04-22], [user:Akulyat,2020-04-22], [user:okwedook,2020-04-22], [user:Minnakhmetov,2020-04-22], [user:Dan389,2020-04-22], [user:Zakoden,2020-04-22], [user:Jostic11,2020-04-22], [user:Nakinamo,2020-04-22], [user:4qqqq,2020-04-22] и [user:allisyonok,2020-04-22] for testing problems and good advice, [user:isaf27,2020-04-22] for round coordination and help with preparation and [user:MikeMirzayanov,2020-04-22] for great systems Codeforces and Polygon.
You will be given 6 problems in both divisions and 2.5 hours to solve them. Please, rea...
decided to make **Div1 round unrated, Div2 round is still rated.** You can
read more details in [this
Announcement of Codeforces Round 637 (Div. 1) - Thanks, Ivan Belonogov!
Announcement of Codeforces Round 637 (Div. 2) - Thanks, Ivan Belonogov!
188.
Kotlin Heroes: Episode 4 <img src="/predownloaded/d3/f6/d3f67b5afe94939d82d9358aeb7a0edcf6a8d33f.png" style="width:300px;float:right;margin:0 1em 1em 1em;"/>
Hello, Codeforces!
First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the first, second and third Kotlin Heroes competitions which were held previously.
Congratulations to the top 3 winners:
**Episode 1**
1. [user:Petr,2020-02-26]
1. [user:ecnerwala,2020-02-26]
1. [user:eatmore,2020-02-26]
**Episode 2**
1. [user:tourist,2020-02-26]
1. [user:eatmore,2020-02-26]
1. [user:Benq,2020-02-26]
**Episode 3**
1. [user:Egor,2020-05-23]
1. [user:tourist,2020-05-23]
1. [user:Benq,2020-05-23]
Ready to challenge yourself to do better? The fourth "Kotlin Heroes" competition will be hosted on the Codeforces platform
on [contest_time:1346]. The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard...
* The round is unrated. * The contest will have 9 problems of various levels of
complexity. * You
Announcement of Kotlin Heroes: Episode 4
Announcement of Kotlin Heroes: Practice 4
189.
The Quarantine Contest Hola, budding coders of the IIT Madras and Codeforces!
On [contest_time:360591], [Programming Club IIT Madras](http://cfi.iitm.ac.in/club/Programming%20Club) will host [The Quarantine Contest](https://codeforces.com/contestInvitation/1d2ebb28034de18f96318fa986b327ea11c701be) and we would like to invite all of you for the same.
The contest is hosted as a reminder to IITM students who are at their Quarantine Hostels, to follow all the safety protocols. It will be a combined **unrated** round for all divisions : )
The contest consists of 8-9 problems [ICPC Style Scoring] to be solved in 150 minutes. While all the problems will be exciting and fun for the participants of the Camp, we believe that the first 4 problems would be easy for the experienced coders & the later problems would be challenging for all.
The round will provide a good range of problems in terms of difficulty, and every problem would definitely be thrilling for the Participants.
The prizes for the **Officia...
all the safety protocols. It will be a combined **unrated** round for all
divisions : )
190.
Codeforces Round #543 and Technocup 2019 Final Round Editorial We are sorry for not having controlled the situation about the streamed editorial and also for the broadcast message about an unethical behaviour of someone from community: here is [explanatory comment](https://codeforces.com/blog/entry/65664?#comment-496450) to the message. When we tried to move the casino problem one position below, something went wrong leading to it being moved one position above (however, [user:Radewoosh,2019-03-04] didn't seem to feel that something was wrong, congratulations!).
Nevertheless, we hope that you liked the problems, and those of you who decided to do something else after you knew that the round was made unrated can solve the problems when convenient (if they wish).
<spoiler summary="Problem A of final/div2 (Technogoblet of Fire)">
[tutorial:1121A]
</spoiler>
<spoiler summary="Problem B of div2 (Mike and Children)">
[tutorial:1121B]
</spoiler>
<spoiler summary="Problem B of final/C div2 (System Testing)">
[tutorial:1121C]
</spoiler>
...
else after you knew that the round was made unrated can solve the problems
when convenient (if they
Tutorial of Technocup 2019 - Final
191.
Codeforces Marathon Round 1 Hi all!
I invite you to take part in Codeforces Marathon Round 1.
It is an unrated contest in which the participants will have to solve
one problem as best as they can.
The problem is presumed not to have a fast full solution.
A score is given for each individual test
according to the quality of the answer found.
The goal is to get the highest total score.
The contest will go on for 10 days.
The start time is [June 12 at 12:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Codeforces+Marathon+Round+1&iso=20160612T12&p1=3905).
During the main phase of the contest, solutions will be checked
on examples and preliminary tests.
After the main phase is over, the final solution of each contestant
will be checked on the final test set, and the total score for this test set
will determine the final scoreboard.
The 10 top scoring participants, as well as 10 random participants
who achieve a good enough score, will get T-shirts.
The contest is supported by Code...
I invite you to take part in Codeforces Marathon Round 1. It is an unrated
contest in which the
Announcement of Codeforces Marathon Round 1
192.
SPC Round #003 Hola, budding coders of the SPC and Codeforces!
On [contest_time:337838], [Programming Club IIT Madras](http://cfi.iitm.ac.in/club/Programming%20Club) will host The [Speed Programming Contest (SPC) Round #003](https://codeforces.com/group/xK9ngmaNEM/contest/337838) and we would like to invite all of you for the same.
To register for the contest: [Click Here](https://codeforces.com/contestInvitation/205bc917cbe2a2aadff6424228fcc04b027cb683)
This is the third round of the 2021 series of Summer Programming Camp. It will be a combined **unrated** round for all divisions : )
The contest consists of 10 problems [ICPC Style Scoring] to be solved in 120 minutes. While all the problems should be exciting and fun for the participants of the Camp, we believe that the first 6 problems should be easy for the experienced coders, the next 3 should be somewhat challenging, while the last problem might need some time even for a Master to solve.
The prizes for the **Official Participants*...
**unrated** round for all divisions : )
193.
Week 2-24 It's been 6 months since I've registered for codeforces and I've decided to continue updating my progress! Big thanks to [user:SecondThread,2022-09-09] for the support shown in my first blog.
#### Overall Changes
154 problems solved(+~134 problems), 1154 rating(from unrated), Switched from python to Java (learning AP Computer Science A)! I've also done ~80 problems on usaco guide and usaco and participated in 40 cf contests(rated and unrated), I try to participate in every contest I could attend. Generally the style of codeforces problems appealed more to me than other competitive programing sites.
Although I haven't gotten much better at solving harder problems, I've become much better at implementing algorithms. Still have a long way to go from here.
Week 2-6
------------------
Best solve: [submission:151053765]
First time solving C and D in a diff 2 contest(upsolving)(and also haven't been able to do this since). Got very lucky with figuring out the quirks of the pr...
154 problems solved(+~134 problems), 1154 rating(from unrated), Switched from
python to Java
194.
2014-2015 ACM-ICPC, NEERC, Southern Subregional Contest (Online Mirror, ACM-ICPC Rules, Teams Preferred) **The contest has been moved to the Gym.**
Today it will be ACM-ICPC, NEEERC, Southern Subregional Contest! As a head of judges I wish good luck to all the participants!
* standings link: http://contest.sgu.ru/monitor/?id=1
On Saturday (October, 25), 07:00 (UTC) it will be a internet-mirror: [contest:481]. Interesting problems are waiting for you. Judges tried to prepare problems of wide difficulty range: for newcomers and for expirienced teams.
For sure, it will be unrated contest. We recommend you to take part in teams. I think, the contest will be moved to Gym later.
Good luck!
[user:MikeMirzayanov,2014-10-21], head of judges.
##### P.S. Saratov Views:
<img src="http://assets.codeforces.com/images/sgu-10k.jpg" style="margin:1em;"/>
<img src="http://assets.codeforces.com/images/saratov-kons.jpg" style="margin:1em;"/>
<img src="http://assets.codeforces.com/images/saratov-bridge.jpg" style="margin:1em;"/>
<img src="http://assets.codeforces.com/images/saratov-...
For sure, it will be unrated contest. We recommend you to take part in teams. I
think, the contest
Announcement of 2014-2015 ACM-ICPC, NEERC, Southern Subregional Contest
195.
AIM Tech Mini Marathon 1 Hey Codeforces!
We’d like to invite you to take part in our **AIM Tech Mini Marathon 1** to be held [this Thursday on the 1st of February at 7 pm MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=1&month=2&year=2018&hour=19&min=0&sec=0&p1=166).
This is **unrated competition**. All the participants will be challenged with only one problem, which doesn’t have a fast and full solution and 3 hours to solve it. Solutions will be evaluated independently on each test. The exact formula of points per test will be given in the problem statement. The score for the contest is a sum of scores for each test. You can participate in contest as a team, 3 members maximum.
**All the tests will be released at the very beginning of the competition**. They will be used both for preliminary and final testing. You will be also provided with a checker and a visualizer, written in Python3. You can find environme...
This is **unrated competition**. All the participants will be challenged with
only one problem
196.
Invitation to TheForces Round #15 (Yummy-Forces) Hello Codeforces!!
We're honored to invite you to **[TheForces Round #15 (Yummy-Forces)](https://codeforces.com/contestInvitation/5ce5fa91d702d465b1f7411809df4bf2120af6e9)** which will take place on **[contest_time:104408]**.
<spoiler summary="What is a TheForces Round?">
TheForces Rounds are series of **unrated contests** which are created by a group of CP lovers in the CF community. You can join our discord server with more than 1000 members for more information about the contests: https://discord.gg/h9N2vGmwep
</spoiler>
**Don't forget the time, registration is open now!, sorry for the inconveniences, the problems are available + $5$ minutes extra time**
You will have **2 hours and 15 minutes** to solve **6** problems.
- Problems were prepared and authored by: [user:-kirito-,2023-06-03], [user:Parisa_Amiri,2023-05-21], [user:O--O,2023-06-03], [user:traverser_25,2023-06-03].
- Also huge thanks to our **ultrabig** army of testers: [user:physics0523,2023-06-03], [us...
TheForces Rounds are series of **unrated contests
Announcement of TheForces Round #15 (Yummy-Forces)
197.
CCC Final Contest | Programming Club, IIT Madras Hello Codeforces!
On [contest_time:468858], [Programming Club IIT Madras](https://cfi.iitm.ac.in/clubs/programming-club) will be hosting **Competitive Coding Conclave 2023's Final contest** — CCC Final Contest and we would like to invite all of you for the same.
It will be a combined **unrated** round for all divisions. It is a team contest for the official participants — you can participate in a team of 2 or individually.
The contest consists of **12 to 15 problems** [ICPC Style Scoring] to be solved in **120 minutes**, in the format of a _Speed Programming Contest_. We believe the problems will be fun and exciting to solve for the participants!
The contest is of **Div.3 level** but with challenging problems in the end. It will provide a good range of problems in terms of difficulty (from very easy problems to ones that can challenge experts), and every problem will be thrilling for the participants to solve.
The prizes for the participants:
- Top 3 teams from IITM
...
It will be a combined **unrated** round for all divisions. It is a team contest
for the official
198.
April Fools Day Contest 2018 The contest is over; I hope you've enjoyed it :-) Editorial is [here](http://codeforces.com/blog/entry/58681).
----
The 6th April Fools Day Contest will take place on Sunday [April 1st](http://www.timeanddate.com/worldclock/fixedtime.html?day=1&month=4&year=2018&hour=18&min=35&sec=0&p1=166). This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
This year I tried to make the problems less puzzling and more versatile. For example, almost all problems have a statement! And you won't need OEIS this time :-)
In this round you'll be given 7 weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces. To get an idea of what the contest will look like, you can check out the contests of the past years: [2012](http://c...
earned on them), and it will be unrated. You can submit solutions in any
language allowed by
Announcement of April Fools Contest 2018
199.
VeeRoute Marathon announcement Hi all!
From February 29 to March 14, a contest supported by company VeeRoute will be held on Codeforces. VeeRoute is a young and ambitious IT company which specializes in automation of transportation logistics.
Participants will have to solve a certain optimization problem as best as they can. The problem is similar to the ones that are being solved by VeeRoute daily. As the competition format is very different from a standard Codeforces round, the contest will be unrated.
#### Participants
We invite everyone who is fond of interesting programming challenges and well-versed in algorithms and data structures. The contest is for individuals. There are no restrictions on age or division.
#### Prizes
After the final testing is over, the winners will be announced, and the following prizes will be awarded:
* I place — iPhone 6S or Nexus 6P at the winner’s choice.
* II place — any mechanical keyboard by ...
different from a standard Codeforces round, the contest will be unrated.
Announcement of VeeRoute Marathon
200.
ICPC NERC Huawei Challenge — Cloud Scheduling Challenge <img src="/predownloaded/50/6e/506e22d11e9f49d4ad8882c6c1877b5989589e60.png" align="right" style="height: 290px; margin: 10px;" alt="text"/>
Hello everyone!
We are thrilled to invite you to the great event — **ICPC NERC Challenge powered by Huawei 12 — 20 December 2020**.
<center style="margin: 2em"> <a href="https://codeforces.com/contests/1460" style="font-size: 15.0px;padding: 8.0px 14.0px;background-color: rgb(226, 36, 14);color: white;">Join to Challenge</a></center>
This contest is based on some real problems from Huawei Cloud team. The task is simplified, but still very challenging. You need to find a schedule for a variety of realistic problem instances, where the goal will be minimizing two different cost functions. There is a non-trivial tradeoff, decision you have to make, on how to choose what is best for a particular case. You will be provided with examples that can help you to tackle the problem. A good solution may also require diving deeper into ...
of December 12-20. This round is unrated for all participants. Everybody is
welcome to participate
Announcement of NERC Challenge 2020: Marathon
201.
Round #85 (Div. 1 + Div. 2) powered by BOI, unrated Hello, Codeforces!
We're going to host a new contest at [csacademy.com](http://csacademy.com). [Round #85](https://csacademy.com/contest/round-85/) will take place on [Wednesday, August 1st, 15:05:00 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?msg=CS+Academy+Round+%2385&iso=20180801T1505&p1=%3A&ah=2). This contest will be a Div1 + Div2, with **7** tasks of varying difficulty that need to be solved in **2** hours.
This contest is powered by the Balkan Olympiad in Informatics(BOI) meaning that the some of the problems are from BOI. Because of this, the round will be unrated. This does not change the fact that the CSA team is doing it's best to make sure that the contest will be great.
#### Facebook event
We recently created a new Facebook event. If you choose "Interested" [here](https://www.facebook.com/events/595041154190631/), you will be notified before each round we organise from now on.
#### Contest format:
- You will have to solve **7** tasks in **...
Round #85 (Div. 1 + Div. 2) powered by BOI, unrated, problems are from BOI. Because of this, the round will be unrated. This does
not change the fact that
202.
Kotlin Heroes 7 Announcement <img src="/predownloaded/6b/62/6b62332b37519ade4a4d42cb266937c422b64557.png" style="width:500px;float:right;margin:0 1em 1em 1em;"/>
Hello, Codeforces!
First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the five Kotlin Heroes competitions which were held previously: [Episode 1](https://codeforces.com/contests/1170), [Episode 2](https://codeforces.com/contests/1211), [Episode 3](https://codeforces.com/contests/1297), [Episode 4](https://codeforces.com/contests/1346), [Episode 5: ICPC Round](https://codeforces.com/contest/1431), and [Episode 6](https://codeforces.com/contest/1488).
Ready to challenge yourself to do better? The [contest:1533] competition will be hosted on the Codeforces platform on [contest_time:1533]. The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard ones, to make it interesting for seasoned competitive programme...
- The round is unrated. - The contest will have 9 problems of various levels of
complexity. - You
Announcement of Kotlin Heroes: Practice 7
Announcement of Kotlin Heroes: Episode 7
203.
Educational Codeforces Round 18 Hello Codeforces!
Good news! Harbour.Space is supporting the return of a new series of educational rounds on Codeforces!
You can read the details in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
<div style="text-align:center"><img src ="http://codeforces.com/predownloaded/b5/00/b500f462d444675afcbf458ed4d396607277b544.png" /></div>
On [March 27, 17:35 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=27&month=3&year=2017&hour=17&min=35&sec=0&p1=166) will be held Educational Codeforces Round 18.
You will be given 6 problems and 2 hours to solve them. We hope that everyone, both novices and experienced coders, will find something interesting in this contest. The contest will be unrated.
The round was prepared by Mikhail [user:PikMike,2017-03-26] Piklyaev, Mikhail [user:MikeMirzayanov,2017-03-26] Mirzayanov and me. We'd like to thank Maxim [user:HellKitsune,2017-03-27] Finutin and Alexey [user:ashmelev,2017-03-27] Shmelev for testing the...
experienced coders, will find something interesting in this contest. The
contest will beunrated.
Announcement of Educational Codeforces Round 18
204.
Kotlin Heroes 8 Announcement <img src="/predownloaded/dc/3d/dc3d601ff391e638c1f2b20ec167083978099bbe.png" style="width:500px;float:right;margin:0 1em 1em 1em;"/>
Hello, Codeforces!
First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the seven Kotlin Heroes competitions which were held previously: [Episode 1](https://codeforces.com/contests/1170), [Episode 2](https://codeforces.com/contests/1211), [Episode 3](https://codeforces.com/contests/1297), [Episode 4](https://codeforces.com/contests/1346), [Episode 5: ICPC Round](https://codeforces.com/contest/1431), [Episode 6](https://codeforces.com/contest/1488), and [Episode 7](https://codeforces.com/contest/1533).
Ready to challenge yourself to do better? The [contest:1571] competition will be hosted on the Codeforces platform on [contest_time:1571]. The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard ones, to mak...
- The round is unrated. - The contest will have 10 problems of various levels
of complexity
Announcement of Kotlin Heroes: Practice 8
Announcement of Kotlin Heroes: Episode 8
205.
Codeforces Round #650 Div 3 Unrated? I submitted the solution to [problem:1367D] during the contest (**Pretest Passed**).
Later on, someone hacked it, that's fine.
But after analyzing a bit I found my code wasn't even working correctly for TestCase 1, then how did it pass the pretests.
Here is my submission [83979354](https://codeforces.com/contest/1367/submission/83979354), kindly check my output on test1 of testcase1.
<spoiler summary="Input">
- abac
- 3
- 2 1 0
</spoiler>
<spoiler summary="Output">
bba
</spoiler>
I don't have 2 'b's. This shouldn't have passed the checker was wrong itself during the contest.
It must have affected a lot of people as well.
Sorry to say but will this make the contest unrated?
UPD1: As expected my solution is hacked on Testcase 1 itself. The same checker first passes the solution, and later fails the solution on the same Testcase, does that make any sense?
! Bubble Cup is a programming competition organized by [Microsoft Development Center Serbia (MDCS)](https://www.microsoft.com/sr-latn-rs/mdcs). The contest will take place on [Saturday, 22nd of September at 11:00 UTC+2](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Bubble+Cup+11+Finals+-+onsite&iso=20180922T11&p1=35&ah=5) in Belgrade, and will last for 5 hours. Live results will be available on the [official Bubble Cup website](http://www.bubblecup.org/CompetitorsCorner/Finals/358). Results will be frozen during the last hour of the competition. The winners will be announced at the closing ceremony.
The format of the competition is very similar to ACM-ICPC — teams consisting of up to three people are allowed, and they have one computer and five hours to solve problems without partial scoring. Ties are broken using the usual time penalty rules.
...
Both contests will be **unrated**, due to the format and the length of the
mirror being dissimilar
Announcement of Bubble Cup 11 - Finals [Online Mirror, Div. 1]
Announcement of Bubble Cup 11 - Finals [Online Mirror, Div. 2]
207.
Kotlin Heroes 5: ICPC Round Announcement <img src="/predownloaded/62/39/62391c8471a7dc4ca0b2f2da3e7903eefd1f3dc0.png" style="width:500px;float:right;margin:0 1em 1em 1em;"/>
Hello, Codeforces!
First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the first, second, third, and fourth Kotlin Heroes competitions which were held previously: [Episode 1](https://codeforces.com/contests/1170), [Episode 2](https://codeforces.com/contests/1211), [Episode 3](https://codeforces.com/contests/1297) and [Episode 4](https://codeforces.com/contests/1346).
Ready to challenge yourself to do better? The [contest:1431] competition will be hosted on the Codeforces platform on [contest_time:1431]. The contest will last 2 hours 30 minutes and will feature a set of problems from simple ones, designed to be solvable by anyone, to hard ones, to make it interesting for seasoned competitive programmers.
**Prizes:**
**Top three winners will get prizes of $512, $256, and $128 re...
- The round is unrated. - The contest will have 9 problems of various levels of
complexity. - You
Announcement of Kotlin Heroes 5: ICPC Round
Announcement of Kotlin Heroes 5: ICPC Round (Practice)
208.
SPC '22 Final Contest | Programming Club, IIT Madras Hola, coders!
On [Monday, August 15 2022, at 17:05<sup>UTC+5.5</sup>](https://www.timeanddate.com/worldclock/fixedtime.html?msg=SPC+%2722+Final+Contest&iso=20220815T1705&p1=553&ah=2&am=30), [Programming Club IIT Madras](http://cfi.iitm.ac.in/club/Programming%20Club) will be hosting Summer Programming Camp 2022's final contest — SPC Final Contest and we would like to invite all of you for the same.
It will be a combined **unrated** round for all divisions. It is a team contest for the official participants — you can participate in a team of 2 or individually.
The contest consists of 15 problems [ICPC Style Scoring] to be solved in 150 minutes, in the format of a _Speed Programming Contest_. We believe the problems will be fun and exciting to solve for you guys :D
The contest is of Div.3 level but with challenging problems in the end. It will provide a good range of problems in terms of difficulty (from very easy problems to ones that can challenge experts), and e...
It will be a combined **unrated** round for all divisions. It is a team contest
for the official
209.
Experimental Educational Round: VolBIT Formulas Blitz Hello, Codeforces!
“Experimental Educational Round: VolBIT Formulas Blitz” will take place on [February <b>18</b>, 2016 at <b>18</b>:00 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Experimental+Education+Round%3A+VolBIT+Formulas+Blitz&iso=20160218T15). This time the problemset is recommended for Div.2 participants.
The round will be unrated for all users and it will be held according to the standard ACM-ICPC rules. You will have **180** minutes (three hours) to solve **18** problems. There will be no open hacks phase after the round.
Our main target audience is beginners and Div. 2 members. All offered problems can be solved without conditional constructs and without loops. Only formulas are required. Assignments and functions can be used to reduce code duplication.
The topics of the problems are:
- combinatorics
- geometry
- game theory
- sequences
- other
The round is created as a part of [Vologda BIT event](https://vk.com/volbit35), also as pa...
The round will be unrated for all users and it will be held according to the
standard ACM-ICPC
210.
[Invitation, Prizes!] CodeRed and Humblefool Cup 2024 by IIIT Allahabad Hello Codeforces!
After the great success of [Alkhwarizm 2024](https://www.codechef.com/START122), we are excited to invite you all to the following two flagship coding events of **Aparoksha** — the annual tech-fest of IIIT Allahabad.
- CodeRed
- Humblefool Cup
Participation is open to all, but the prizes are only for Indian university/school students. We encourage everyone to participate in these contests. All of these contests are **unrated** and will be held as **CodeForces gym** contest.
<img src="/predownloaded/5a/1e/5a1ea2614ccd6783e6fb2189f29479dee7939232.png" style="float: right;margin: 0 1.0% 5.0%;width: 48.0%;height: 48.0%;max-width: 60.0%;max-height: 60.0%;">
<img src="/predownloaded/cf/ba/cfbad826e78ebd0b3251ef43907ee7811e21ef4d.png" style="float: left;margin: 0 1.0% 5.0%;width: 48.0%;height: 48.0%;max-width: 60.0%;max-height: 60.0%;">
____________________________________________________________________________________________________________________
...
encourage everyone to participate in these contests. All of these contests are
**unrated** and will be
211.
Codeforces Round #457 (Div. 2) Editorial I would like to take this opportunity to express my deepest apology to all of you who take your own precious time to participate in this unrated round. Also, apologies to [user:gritukan,2018-01-19] who really helped a lot in preparing the round and [user:MikeMirzayanov,2018-01-19] who helped to host the round, I did not do a good job in managing the round. As the main author of this round, I'm undoubtedly responsible for the mistake that not writing a brute force solution to test the correctness of the intended solution. It is my responsibility to make sure everything is right before the round starts. I am really sorry that the round must be unrated to ensure fairness to all contestants.
I hope all of you can learn something from the contest. Do not claim a greedy solution absolutely correct (like me :C) unless you have proved it. On the bright side, I'm really glad that some of you found problem D and E interesting as said in some comments in the announcement blog post. I admit tha...
precious time to participate in this unrated round. Also, apologies to
[user:gritukan,2018-01-19
Tutorial of Codeforces Round 457 (Div. 2)
212.
Surprise Language Round #5 The round is over, I hope you have enjoyed it. [Here](http://codeforces.com/blog/entry/3948) is the editorial.
The language of this round is COBOL (dialect COBOL85), one of the oldest programming languages (date of “birth”: 1959, so it’s twice older than I am). Despite being so old, it’s still in active use, though not in programming competitions, so I think it should be enough of a surprise for you :-)
The problem "A+B" (numbers A and B given in separate lines) can be solved in a following way:
~~~
IDENTIFICATION DIVISION.
PROGRAM-ID. SOLUTION.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 A PIC 9(10) VALUE ZEROES.
01 B PIC 9(10) VALUE ZEROES.
01 STR PIC X(10).
PROCEDURE DIVISION.
ACCEPT STR
MOVE STR TO A
ACCEPT STR
MOVE STR TO B
ADD A TO B
DISPLAY B
STOP RUN.
~~~
[cut]
The first 7 characters of each line must be ...
- This round will be unrated and it will use ACM ICPC rules. - It will have 5
problems, sorted by
Announcement of Surprise Language Round 5
213.
Invitation to TOKI Mirror Open Contest: BNPC-HS 2021 Final Round <p align="center"><img src="https://i.imgur.com/JpX9oOj.png"></p>
We are excited to invite you to [TOKI Mirror Open Contest (Unrated) — BNPC-HS 2021 Final Round](https://tlx.toki.id/contests/tmoc-bnpchs-2021-final) on [Saturday, October 16th 2021 13:05 UTC+7](https://www.timeanddate.com/worldclock/fixedtime.html?msg=BNPC-HS+2021+Final+Round+Mirror&iso=20211016T1305&p1=108&ah=5). The contest will be **5 hours** long and will feature **10 problems**. Note that you should participate in the contest **individually**. Scoring will be based on **ICPC rules**.
The problems were written by [user:KerakTelor,2021-10-11], [user:Owmicron,2021-10-11], [user:Yoshiyuki,2021-10-11], [user:siplusplus,2021-10-11], [user:rfpermen,2021-10-11], [user:Berted,2021-10-11], [user:Nich728,2021-10-11], [user:VinsenN,2021-10-11], and [user:vioalbert,2021-10-11].
Problem components were prepared by the Scientific Committee: [user:rfpermen,2021-10-11], [user:Owmicron,2021-10-11], [user:ZeroScar,2021-...
We are excited to invite you to [TOKI Mirror Open Contest (Unrated) — BNPC-HS
2021 Final
214.
Unusual Testing Round (IFrame) Hello, Codeforces.
**UPD: Round is finished. Thank you for your participation. <a href="/alpha7#/contest/7/standings">Final results</a>.**
Today ([16:00 UTC](http://www.timeanddate.com/worldclock/fixedtime.html?day=2&month=4&year=2014&hour=20&min=0&sec=0&p1=166)) we want you to take part in testing and unrated round with unussual scoring system. With your help we want to test new scoring, new type of problems and Codeforces system inside `<iframe>` tag.
Start time is **[16:00 UTC](http://www.timeanddate.com/worldclock/fixedtime.html?day=2&month=4&year=2014&hour=20&min=0&sec=0&p1=166)**
<a style="font-size:2em;" href="/alpha7">Go to the Contest!</a>
There are two types of problems: logic puzzles and programming tasks.
A logic puzzle is a task that is designed to be solved by hand (but it is not forbidden to write some helper code to do this). Each logic puzzle consists of one or more tests. Each question can be answered separately from the others.
There is a "Submit" ...
&hour=20&min=0&sec=0&p1=166)) we want you to take part in testing and unrated
round with unussual
215.
Codeforces Contests <p><i>You may read complete rules <a href="/blog/entry/4088">here</a>.</i></p>
<img src="http://static.codeforces.ru/cache/images/codeforces-logo.png" style="float:right;margin:0.5em;">
<p>
The text contains only preliminary rules of Codeforces contests - something surely will change. In particular, I hope to help the community to find the illogic in the rules. However, I have already discussed the format with programming contests dinosaurs and made unrated alpha contests - it seems rules are OK.
</p>
<p>
I think than the format 5 tasks x 2 hour is quite good. For this reason, in the near future we will not change it, but of course, experiments are possible.
</p>
<p><b>
1.</b> Before the competition all participants are divided into rooms, each room contains about 20 participants. For now random strategy works, but after a while it will be somehow correlated with the rating.[cut]</p>
<p><b>
2.</b> The start of contest looks quite like ICPC: all problems immediately...
already discussed the format with programming contests dinosaurs and made
unrated alpha contests - it
216.
Kotlin Heroes 9 Announcement <img src="/predownloaded/dc/3d/dc3d601ff391e638c1f2b20ec167083978099bbe.png" style="width:500px;float:right;margin:0 1em 1em 1em;"/>
**Given the current circumstances, we have decided to postpone Kotlin Heroes until further notice. Thank you for your understanding.**
Hello, Codeforces!
First and foremost, we would like to say a massive thank you to everyone who entered and submitted their answers to the eight Kotlin Heroes competitions which were held previously: [Episode 1](https://codeforces.com/contests/1170), [Episode 2](https://codeforces.com/contests/1211), [Episode 3](https://codeforces.com/contests/1297), [Episode 4](https://codeforces.com/contests/1346), [Episode 5: ICPC Round](https://codeforces.com/contest/1431), [Episode 6](https://codeforces.com/contest/1488), [Episode 7](https://codeforces.com/contest/1533), and [Episode 8](https://codeforces.com/contest/1571).
Ready to challenge yourself to do better? The [contest:1643] competition will be hosted on the Codef...
- The round is unrated. - The contest will have 9 or 10 problems of various
levels of complexity
217.
Codeforces Round #365 (Div. 2) Hi everyone!
Codeforces Round #365 (Div.2) takes place today on [4th of August at 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Codeforces+Round+%23365+%28Div.+2%29&iso=20160804T1805&p1=349). As usual Div.1 participants can join out of competition.
I am the author of all the problems, and this is my first round on Codeforces. I advise you to read all the problems, hope you will enjoy them :)
I'd like to thank [user:GlebsHP,2016-08-04] and [user:dans,2016-08-04] for helping me in preparing problems, [user:MikeMirzayanov,2016-08-04] for the great Codeforces and Polygon platforms and [user:IlyaLos,2016-08-04] for some useful adviсe.
In this round you will meet Mishka, a little polar bear. She is still young, that's why she may have some problems in finding answers for difficult questions. Will you help her to cope with some of them? :)
**UPD.** 5 problems, 2 hours to solve them and scoring distribution: **500 — 1000 — 1750 — 2000 &...
**UPD.** Round is **unrated**.
Announcement of Codeforces Round 365 (Div. 2)
218.
Shaastra Programming Contest 
Hello Everyone!
On [Saturday, December 26, 2022, at 18:00<sup>UTC+5.5</sup>](https://www.timeanddate.com/worldclock/fixedtime.html?msg=Shaastra+Programming+Contest&iso=20221226T18&p1=553&ah=2), Coding and Logic vertical of [Shaastra](https://shaastra.org/) will be hosting **Shaastra Programming Contest**, and we would like to invite all of you for the same.
Contest Link: [click here]( cutt.ly/SPC_Prelims )
cutt.ly/SPC_Prelims
Fill this form to be considered eligible for participation certificate and prizes — [click here](https://forms.gle/UEpZ6MnV6F5xw3en9) **Note**: Registration on unstop is compulsory but not sufficient.
It will be a combined **unrated** round for all divisions. You can participate in a team of 2 or individually.
[Click here](https://cutt.ly/SPC_Registration) to register for the contest.
**Note**: Only students who have registered will be eligible for prizes.
The...
It will be a combined **unrated** round for all divisions. You can participate
in a team of 2 or
219.
VRt Contest 2019 Announcement Hi all!
From April 30th to May 14th, Codeforces will host VRt Contest:
the second contest organized by VeeRoute.
VeeRoute is the developer of planning and management software
for transportation and multimodal logistics.
Contest participants will have to solve an optimization problem
where local optimization is challenging.
The task is similar to those that VeeRoute has to solve regularly.
Since the format is nothing like a standard Codeforces round,
the contest will be unrated.
### Participation
Everyone is welcome to take part in the contest.
The consest is for individual participation,
with no restrictions on age or division.
### Prizes
* I place — 75 000 RUB (1155 USD)
* II place — 50 000 RUB (770 USD)
* III place — 25 000 RUB (385 USD)
Additionally, top 25 participants will get a VRt T-shirt.
Good luck to all participants, and have a great contest...
nothing like a standard Codeforces round, the contest will be unrated.
Announcement of VRt Contest 2019 (marathon)
220.
April Fools Day Contest 2019 The contest is over; I hope at least some of you enjoyed it :-) The editorial is published [here](http://codeforces.com/blog/entry/66327).
---
The 7th April Fools Day Contest will take place on Monday [April 1st](https://www.timeanddate.com/worldclock/fixedtime.html?day=1&month=4&year=2019&hour=18&min=5&sec=0&p1=166). This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.
In this round you'll be given several weird problems and 2 hours to solve them. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them), and it will be unrated. You can submit solutions in any language allowed by Codeforces. To get an idea of what the contest will look like, you can check out the contests of the past years: [2012](http://codeforces.com/contest/171), [2013](http://codeforces.com/contest/290), [2014](http://codeforces.com/contest/409), [2016](http://code...
time earned on them), and it will be unrated. You can submit solutions in any
language allowed by
Announcement of April Fools Day Contest 2019
221.
Codeforces Round #325 Hi, Codeforces!
Codeforces Round #325 will take place on [October 12, 2015 at 09:00 UTC](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Codeforces+Round+%23325&iso=20151012T0900) for the first and second divisions. Please note that the round will start at unusual time!
The problems of this round are taken from the Regional stage of the All-Russian school team programming olympiad that will be at the same time in Saratov, Russia. Lets wish school teams good luck on competition!
The problemset for school olympiad differs from problems that will be on round. In addition in problemset for school olympiad there will be some problems, which are not included in the round and vice versa. So don't be frightened by the difficulty of problems given for school teams :-)
The process of problems preapring was very interesting: we were reworking problem statements many times, adding tests, changing limits, even managed to change fully prepared problem with another (we had to sto...
will discuss the question to make round unrated only for that participant. We
are apologize to
Announcement of Codeforces Round 325 (Div. 1)
222.
CROC-MBTU 2012, Elimination Round Good day!
Elimination round of the CROC Collegiate Programming Competition for the MSTU Bauman students is going to be here soon. The official championship participants will take part in the competition, all others will be out of the competition in the table of results.
The contest is held by the well-known rules ACM-ICPC. Competition duration is 2:00 hours. Supported programming languages are C/C++, Pascal, Java, C#, Python, Ruby, PHP, Haskell, Scala, OCaml, and D.
This Round will be the rated for the Div-2 participants, regardless of whether one is the competition championship party or not. For Div-1 participants this round is unrated.
Please note that the official participants of the competition are not need to register for this competition they will be registered automatically (with advance registration at [website] (http://www.crocok.ru/championship/)).
Good luck to everyone!
**UPD.** Competition is completed, thank you very much for your participation! I hope th...
competition championship party or not. For Div-1 participants this round is
unrated.
Announcement of CROC-MBTU 2012, Elimination Round (ACM-ICPC)
223.
Online mirror of The 2023 ICPC Asia Jakarta Regional Contest Hello Codeforces!
We are going to hold The 2023 ICPC Asia Jakarta Regional Contest.
We invite you to join the online mirror contest [2023-2024 ICPC, Asia Jakarta Regional Contest (Online Mirror, Unrated, ICPC Rules, Teams Preferred)](https://codeforces.com/contests/1906) on Codeforces. It will be held on [contest_time:1906] and will last for 5 hours.
The mirror will be held using ICPC-style scoring with 10 to 13 problems. The problem statements will only be available in English. We encourage participating as a team using only one computer for coding (as in ICPC contests). The mirror will be unrated.
Some useful links:
* [The 2023 ICPC Asia Jakarta homepage](https://competition.binus.ac.id/icpc2023)
* [The regional information in ICPC Global](https://icpc.global/regionals/finder/Jakarta)
* [The onsite scoreboard](https://competition.binus.ac.id/contest/public)
We hope that you will enjoy the contest. Good luck and have fun!
**UPD.** The mirror has started! You can...
(Online Mirror, Unrated, ICPC Rules, Teams
Preferred)](https://codeforces.com/contests/1906) on, coding (as in ICPC contests). The mirror will be unrated.
224.
Mirror of Bubble Cup X Finals on Codeforces Hi Codeforces!
It's our pleasure to announce the 10th edition of Bubble Cup. Bubble Cup is a programing competition organized by [Microsoft Development Center Serbia (MDCS)](https://www.microsoft.com/sr-latn-rs/mdcs), and will be held this weekend. Contest will take place on [Saturday, 2nd of September at 09:30 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?day=2&month=9&year=2017&hour=9&min=30&sec=0), in Belgrade, Serbia. Live results will be available on [the official Bubble Cup website](http://bubblecup.org/CompetitorsCorner/Results/Live) (results will be frozen during the last hour of the competition). Winners will be announced at the closing ceremony.
Just like the two previous editions, this final will be followed by an online mirror competition on Codeforces. Mirror will take place on [Sunday, 3rd of September at 10:00 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?day=3&month=9&year=2017&hour=10&min=0&sec=0). Contest will last for 5 hours and ACM I...
The contest will be unrated. The reason for this is because rules of this
contest are not common
Announcement of Bubble Cup X - Finals [Online Mirror]
225.
Unknown Language Round #4 <p>The round is over; I hope you enjoyed it. <a href="http://codeforces.com/blog/entry/3226">Here</a> is the editorial.</p>
<br />
<p>The language of this round is Befunge, a lovely two-dimensional esoteric language. It's quite neat and convenient, especially for an esoteric language. Thus, for example, "A+B" problem, where A and B are given in separate lines, can be solved like this:</p>
<pre>&&+.@</pre>
<p>To learn the language you can read <a href="http://catseye.tc/projects/befunge93/">the original documentation</a> (the rumor is that it is broken in some browsers), examples of programs at <a href="http://rosettacode.org/wiki/Befunge">Rosetta Code</a> and <a href="http://progopedia.com/language/befunge/">Progopedia article</a> with annotated examples.</p>
<p>Our testing system uses <a href="https://github.com/programble/befungee">befungee</a> interpreter, which implements Befunge-93 dialect. To run the interpreter, one needs to have Python installed (version 2.6...
* This round will be unrated and it will use ACM ICPC rules.
* It will have 10
Announcement of Unknown Language Round 4
226.
Educational Codeforces Round #1 Hi, Codeforces!
Educational Codeforces Round #1 will take place on [13 ноября 2015 года в 18:00 MSK](http://www.timeanddate.com/worldclock/fixedtime.html?msg=Educational+Codeforces+Round+%231&iso=20151113T1500) for the first and second divisions. You can read about educational rounds [here](http://codeforces.com/blog/entry/21496).
The round will be unrated for all users and it will be held with extented ACM ICPC rules. You will have two hours to solve five problems. After that you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
Educational rounds are (and would) be prepared by me, Edvard Davtyan from Saratov SU Daemons team. Problems was invented by me and [user:MikeMirzayanov,2015-11-13]. Thanks to my teammate [user:dans,2015-11-13] for testing problems and [user:MikeMirzayanov,2015-11-13] for Codeforces, Polygon and idea of the educational rounds.
I hope you will enjoy the problems. If they will be too simple...
The round will be unrated for all users and it will be held with extented ACM
ICPC rules. You will
Announcement of Educational Codeforces Round 1
227.
Educational Codeforces Round 29 Hello Codeforces!
On [September 21, 18:05 MSK](https://www.timeanddate.com/worldclock/fixedtime.html?day=21&month=9&year=2017&hour=18&min=5&sec=0&p1=166) Educational Codeforces Round 29 will start.
Series of Educational Rounds continue being held as [Harbour.Space University](https://harbour.space/) initiative! You can read the details about the cooperation between [Harbour.Space University](https://harbour.space/) and Codeforces in the <a href="http://codeforces.com/blog/entry/51208">blog post</a>.
The round will be **unrated** for all users and will be held on extented ACM ICPC rules. After the end of the contest you will have one day to hack any solution you want. You will have access to copy any solution and test it locally.
You will be given **7 problems** and **2 hours** to solve them.
The problems were prepared by Mikhail [user:PikMike,2017-09-20] Piklyaev, Mikhail [user:MikeMirzayanov,2017-09-20] Mirzayanov, Vladimir [user:0n25,2017-09-21] Petrov and me.
Good...
The round will be **unrated** for all users and will be held on extented ACM
ICPC rules. After the
Announcement of Educational Codeforces Round 29
228.
UTPC April Fool's Contest 2024 Hello, Codeforces!
[UTPC](https://www.cs.utexas.edu/users/utpc/index.html), the competitive programming organization at the University of Texas at Austin, is happy to invite you to participate in our first ever April Fool's contest which will be held on [Monday, April 1, 2024 at 6:00PM UTC-5 (CDT)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=UTPC+April+Fool%27s+Contest+2024&iso=20240401T18&p1=24&ah=2).
You will be given many wacky problems and 2 hours to solve them, with standard ICPC scoring. Anyone is welcome to participate! This is a **team** contest, meaning that you are allowed to compete in teams of up to 3 members (it is totally acceptable to compete without teammates as well). This is (of course) not an official Codeforces round, and is thus unrated.
Prizes will be available to UT students competing in person in Austin (at the Gates-Dell Complex), or online.
The problems were prepared and tested by [user:mwen,2024-03-29], [user:fishy15,2024-03-29], [us...
course) not an official Codeforces round, and is thus unrated.
Announcement of UTPC April Fools Contest 2024
229.
Unusual Testing Round 3 Hello,
Once again I'd like to host unusual unrated round. With your help we want to test untypical scoring system and unusual problems.
The contest will start today on [18:30 (UTC)](http://www.timeanddate.com/worldclock/fixedtime.html?day=30&month=4&year=2014&hour=22&min=30&sec=0&p1=166). We will add large and bright special link to enter into the contest area. The contest duration is 90 minutes. But it will be easy problems and hope that many participants will solve all of them before the end.
<br>
<span style="font-size:2em;">[Go to the Contest →](/alpha49)</span>
<br><br>
It will be two types of problems: logic puzzles and programming tasks.
A logic puzzle is a task that is designed to be solved by hand (but it is not forbidden to write some helper code to do this). Each logic puzzle consists of one or more tests. Each question can be answered separately from the others. There is a "Submit" button below each test. To answer the question, press "Submit" button...
Once again I'd like to host unusual unrated round. With your help we want to
test untypical scoring
230.
ICPC Communication Routing Challenge — powered by Huawei <img src="/predownloaded/aa/57/aa577c257884a5ae68792513c31d9f64fd7bff5f.png" align="right" style="height: 270px; margin: 10px 20px 20px;" alt="text"/>
**Hello, Codeforces!**
Welcome to the ICPC Communication Routing Challenge powered by Huawei!
This challenge edition is very special, as it will be happening in conjunction with the ICPC World Finals!
For those who are not participating in the finals — ICPC and Codeforces are offering a unique chance to compete during a **5-day Challenge Marathon** and win amazing prizes from Huawei!
**ICPC Challenge Marathon (open to public, unrated): [October 9-14, 2021, 00:00 UTC](https://www.timeanddate.com/worldclock/fixedtime.html?msg=2021+ICPC+Communication+Routing+Challenge&iso=20211009T00&p1=1440):**
<center style="margin: 2em;"> <a href="https://codeforces.com/contests/1576" style="text-decoration: none;font-size: 18.0px;background-color: rgb(207, 56, 34);color: white;font-weight: bold;padding: 0.5em 1.0em;">REGISTER</a>
...
**ICPC Challenge Marathon (open to public, unrated): [October 9-14, 2021, 00:00
UTC](https
Announcement of 2021 ICPC Communication Routing Challenge: Marathon
231.
ICPC Amritapuri Practice Session #7 [Team Contest] Announcement Hello Codeforces,
**ICPC Amritapuri** Regional will be hosting next team practice round on [CodeDrills](https://codedrills.io/contests/amrita-icpc-practice-session-7) on [Tuesday, 25th May 2021](https://www.timeanddate.com/worldclock/fixedtime.html?msg=ICPC+Amritapuri+Practice+Session+%237&iso=20210525T1830&p1=438&ah=2&am=30). There will be 5 problems to be solved in 2.5 hours.
**Contest Details**
* Contest Link — [Amritapuri Practice Session #7](https://codedrills.io/contests/amrita-icpc-practice-session-7)
* Date & Time — [25 May 2021, Tuesday, 18:30 IST](https://www.timeanddate.com/worldclock/fixedtime.html?msg=ICPC+Amritapuri+Practice+Session+%237&iso=20210525T1830&p1=438&ah=2&am=30)
* Duration — 2.5 Hours
* Will follow standard ICPC scoring system (20 minutes penalty and 1 point per problem)
* It is a team contest and it would be unrated.
**Registration**
* You will need to create a tea...
per problem) * It is a team contest and it would be unrated.
Codeforces (c) Copyright 2010-2024 Mike Mirzayanov
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