Codeforces Round #305 Codeforces round #305 is gonna take place [soon](http://timeanddate.com/worldclock/fixedtime.html?day=26&month=5&year=2015&hour=19&min=30&sec=0&p1=166) and I'm the writer. After my previous contest that many people think it was a hard contest, I prepared an easy contest to cheer you up! I want to thank [user:Haghani,2015-05-18] for testing this round, [user:Zlobober,2015-05-18] for help me prepare this round and his great advises, [user:Delinur,2015-05-20] for translating problem statements into Russian, [user:mruxim,2015-05-18] and Yasser Ahmadi Phoulady (Rasta) for their advises and ideas, [user:Swift,2015-05-18] for helping me choose legends and graphics and [user:MikeMirzayanov,2015-05-18] for great Codeforces and Polygon platform and guys from Physics Olympiad that kept disturbing me while preparing this round. This is my second official round and I hope you enjoy it. The main character of this round is gonna be Mike (I didn't say [user:MikeMirzayanov,2015-05-18] :D). ...

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Hybrid Tutorial #-1: Heavy-Light Decomposition **[Here](https://www.youtube.com/watch?v=_G_LMuLWMaI&list=PLDjGkpToBsYDx4GWu2u87sTqt6ICELz-T) is a playlist of all hybrid tutorials I've done.** # "Intro" _Timestamp: [00:00](https://youtu.be/_G_LMuLWMaI)_ Hi! Definitely not inspired by [this comment](https://codeforces.com/blog/entry/81086?#comment-675431), I've decided to try something that seems relatively novel — combining a blog and video tutorial into one, in a "hybrid" fashion. Both should be usable independently, but they will have the same "flow" and structure so you can reference both for concepts that are harder to grasp, and the two will supplement each other. The goal of these is to be **complete** — beneficial for both video and blog lovers, as well as full of enough information that anyone without much of an idea of what the concept is should be able to fully understand. There will be code as well, however, I very highly recommend not looking at it, but rather working out the implementation for yours...

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Educational Codeforces Round 52 Editorial [problem:1065A] <spoiler summary="Tutorial"> [tutorial:1065A] </spoiler> <spoiler summary="Solution (Ajosteen)"> ~~~~~ #include <bits/stdc++.h> using namespace std; int main() { int s, a, b, c; int t; cin >> t; for(int i = 0; i < t; ++i){ cin >> s >> a >> b >> c; s /= c; int x = s / a; s %= a; long long res = x * 1LL * (a + b); res += s; cout << res << endl; } return 0; } ~~~~~ </spoiler> [problem:1065B] <spoiler summary="Tutorial"> [tutorial:1065B] </spoiler> <spoiler summary="Solution (Ajosteen)"> ~~~~~ #include <bits/stdc++.h> using namespace std; int main() { int n; long long m; cin >> n >> m; long long cur = 1; long long rem = m; while(rem > 0){ long long d = min(cur, rem); rem -= d; ++cur; } assert(rem == 0); long long res = n; if(cur > 1) re...

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Codeforces Round #421 Editorial First, I apologize for problems with round and serious problem with Div1A/Div2C. It was very important round for me and, as always, something goes wrong. [user:KAN,2017-06-28] have already [wrote about this](http://codeforces.com/blog/entry/52944). Anyway, there are problems, so editorial must exists. Due some circumstances, Editorial will be upload in parts. Also, most of tutorials will contain main ideas how to solve task, not ready algorithm. [tutorial:820A] <spoiler summary="code"> ~~~~~ #define fore(i, l, r) for(int i = int(l); i < int(r); i++) #define forn(i, n) fore(i, 0, n) int c, l, v0, v1, a; inline bool read() { if(!(cin >> c >> v0 >> v1 >> a >> l)) return false; return true; } inline void solve() { int pos = v0; int t = 1; int add = v0; while(pos < c) { add = min(v1, add + a); pos += add - l; t++; } cout << t << endl; } ~~~~~ </spoiler> [tutorial:820B] <spoiler summary="code"> ~~~~~ int n, a; i...

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Codeforces Round #359 Editorial If you notice typos or errors, please send a private message. <br> <br> [Div2A Free Ice Cream](http://codeforces.com/contest/686/problem/A) <br> Author: [user:cdkrot,2016-06-24] <br> Developer: [user:ch_egor,2016-06-23] <br> You just needed to implement the actions described in statement. <br> If you solution failed, then you probably forgot to use 64-bit integers or made some small mistake. <br> Correct solution: <br> <br> <spoiler summary="C++ code"> ~~~~~ #include <iostream> #include <cstdio> #include <cstdlib> #include <string> #include <cstring> #include <vector> #include <stack> #include <queue> #include <deque> #include <set> #include <map> #include <cassert> #include <algorithm> #include <iomanip> #include <ctime> #include <cmath> #include <bitset> #pragma comment(linker, "/STACK:256000000") using namespace std; typedef long long int int64; typedef long double double80; const int INF = (1 << 29) + 5; const int64 LLINF = (1ll <<...

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What if tourist goes rainboy mode? (Simulation) DISCLAIMER: NO TOURISTS AND RAINBOYS WERE PINGED Ah yes, two names that most people on Codeforces have heard -- <b>t<span style="color:red;">ourist</span></b> and <b><span style="color:purple;">rainboy</span></b>, one known as the CP Legend, and one as the user who does everything reverse. Such a great idea to put them together &mdash; a hypothetical user with the same ability as <b>t<span style="color:red;">ourist</span></b>, and solves problems the <b><span style="color:purple;">rainboy</span></b> way. _For those unaware of the "rainboy way", it means solving the problems in reverse order. In particular, if he cannot solve the final problem, he solves no problems in the contest._ Unfortunately, <b><span style="color:purple;">rainboy</span></b> had not yet reached red, peaking at 2398 rating. How far can this user go? We shall simulate this user through all the contests that tourist and rainboy took part in comparably, which adds up to 60 contests from [contest:745] to [cont...

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Codeforces Round #305 Editorial ### [problem:548A] Consider characters of this string are number 0-based from left to right. If $|s|$ is not a multiply of $k$, then answer is "NO". Otherwise, let $len = \frac{|s|}{k}$. Then answer is "Yes" if and only if for each $i$ that $0 \leq i < |s|$, $s_i = s_{(i/len) * len + len - 1 - (i \% len)}$ where $a\%b$ is the remainder of dividing $a$ by $b$.  Time complexity: $\mathcal O(|s|)$. [C++ Code](http://ideone.com/HpYQHZ) by [user:PrinceOfPersia,2015-05-24] [Python Code](http://ideone.com/A6yhex) by [user:Haghani,2015-05-24] [Python Code](http://ideone.com/PHiL7p) by [user:Zlobober,2015-05-24] ### [problem:548B] Consider this problem: We have a binary sequence $s$ and want to find the maximum number of consecutive 1s in it. How to solve this? Easily: ~~~~~ ans = 0 cur = 0 for i = 1 to n: if s[i] == 0 then cur = 0 else cur = cur + 1 ans = max(ans, cur)...

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Invitation to TOKI Open Contest February 2017 Hi Codeforces Community, I would like to invite you to participate in TOKI Open Contest. TOKI Open Contest is our (Indonesian's) monthly/bi-monthly online contest. Starting this month, we have decided to make this contest international :) Every problem is written in both Bahasa Indonesia and English. TOKI Open Contest February 2017 will be held on [Saturday, 18 February 2017, 19.00 &mdash; 21.00 Western Indonesian Time (UTC+7)](https://www.timeanddate.com/worldclock/fixedtime.html?msg=TOKI+Open+Contest+February+2017&iso=20170218T12&p1=%3A&ah=2). This contest is written by [user:athin,2017-02-08], [user:anthonyhkf,2017-02-08], [user:aguss787,2017-02-08], and [user:jonathanirvings,2017-02-08]. Several details related to the contest: 1. The contest will use ACM-ICPC scoring type. 2. There will be FIVE problems with various difficulties but the weight for each problem is the same. The contest time is 2 hours. 3. Any non-Accepted submission will get 8 minutes penalty (but ...

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View the history of top10 in Codeforces! The video is [here](https://www.bilibili.com/video/av43450831/) (uploaded by myself). [user:Anguei,2019-02-14] helped me upload it [on YouTube](https://youtu.be/nfAnKzyiKTo). Thank [user:I_love_Tanya_Romanova,2019-02-14] for pointing out my mistake of ignoring the inactive users. I have fixed it now. I get the rating history of each user **who is in the top5000 either of the active or the inactive now** by Codeforces API. So if a user was in the top10 but is in neither the top5000 of the active nor the inactive now, he will not be included in the historical top10s. I made the video using [Dynamic Ranking Visualization](https://github.com/Jannchie/Historical-ranking-data-visualization-based-on-d3.js). And the codes written by me is [here](https://github.com/ouuan/Get-CF-Historical-TOP10).  P.S. The numbers change continuously in the video, so the ratings in the picture are not the exact value. P...

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Codeforces Top 100 Comments Hi guys, Here you can find Top 100 Comments in the history of Codeforces Til 1 Jan 2015. It reminds us of some memories we had together in Codeforces :) ### Top 100 [user:yeputons,2015-01-01] 448 http://codeforces.com/blog/entry/8063#comment-138056 [user:zeulb,2015-01-01] 438 http://codeforces.com/blog/entry/10193#comment-156433 [user:Petr,2015-01-01] 354 http://codeforces.com/blog/entry/12605#comment-174158 [user:zakharvoit,2015-01-01] 326 http://codeforces.com/blog/entry/12605#comment-174167 [user:ashmelev,2015-01-01] 318 http://codeforces.com/blog/entry/4302#comment-87389 [user:tourist,2015-01-01] 307 http://codeforces.com/blog/entry/7499#comment-133421 [user:MikeMirzayanov,2015-01-01] 305 http://codeforces.com/blog/entry/1767#comment-33686 [user:Gogis,2015-01-01] 297 http://codeforces.com/blog/entry/15511#comment-204474 [user:sorry_dreamoon,2015-01-01] 287 http://codeforces.com/blog/entry/15336#comment-202752 [user:MikeMirzayanov,2015-01-01] 286 h...

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Educational Codeforces Round 53 [Rated for Div. 2] On [contest_time:1073] [contest:1073] 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,2018-10-24] Glazov, Adilbek [user:adedalic,2018-10-24] Dalabaev, Vladimir [user:Vovuh,2018-10-24] Petrov, Ivan [user:BledDest,2018-...

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Codeforces Round #570 (Div. 3) &lt;almost-copy-pasted-part&gt; Hello! [contest:1183] will start at [contest_time:1183]. You will be offered 6 or 7 problems (or 8) 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 rating 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended ACM-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 &mdash; just like you will be upset if many solutions fail after the contest is over. You will be given 6 or 7 (or 8) problems and 2 hours to solve them. Note that **the penalty** for the wrong submission in this round (and the following Div. 3 rounds) is **10 minutes**. [Remember] (/blog/entry/59228) that only the <i>trusted participants of the third division</i> will be included in the ...

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Поиск по постам на Codeforces Добрый день. Теперь для поиска по постам вам вовсе не обязательно уходить в Google, а можно это делать прямо на Codeforces. Мы поддержали поиск по текстам постов на базе Apache Lucene. В индексе содержатся все открытые публичные посты, которых уже более 15000 штук. Временно поиск по тегам теперь недоступен (но и по тегам заиндексируем), но вместо него вы обнаружите возможность найти посты и даже отсортировать выдачу по нужному критерию. Кстати, язык запросов к поисковику &mdash; это все возможности Lucene, так что можете найти полное описание и писать неочевидные запросы. Можно ввести несколько слов &mdash; все они попадут в требования к поиску (что-то из требований может быть опущено движком, если документов, удовлетворяющих всему запросу нет). Кроме того, осуществляется поиск по словоформам и, если повезет, по синонимам. Поддерживается поиск по названию, автору и специальный синтаксис запросов. Вот примеры запросов: * `305` &mdash; ищет все посты, содержащие 305, най...

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Educational Codeforces Round 87 [Rated for Div. 2] Hello Codeforces! On [contest_time:1354] [contest:1354] will start. **Please notice the unusual time.** 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 Roman [user:Roms,2020-05-15] Glazov, Adilbek [user:adedalic,2020-05-15] Dalabaev, Vladimir [...

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Codeforces Round #355 (Div. 2) Editorial [problem:677A] For each friend we can check, if his height is more than $h$. If it is, then his width is $2$, else $1$. Complexity $O(n)$. <spoiler summary="Code"> ~~~~~ #include <iostream> using namespace std; typedef long long ll; ll i,n,h,ans,x; int main() { cin >> n >> h; ans = n; for (i = 0; i < n; i++) { cin >> x; ans += (x>h); } cout << ans << endl; return 0; } ~~~~~ </spoiler> [problem:677B] The solution, that does same thing, as in the problem statement will fail with TL, because if the height of each piece of potato will be $10^9$ and smashing speed will be $1$, then for each piece we will do $10^9$ operations. With each new piece of potato $a_i$ we will smash the potato till $a[i]$ $MOD$ $k$, so we will waste $a[i]/k$ seconds on it. If we can not put this piece of potato after that, we will waste $1$ more second to smash everything, that inside, else just put this piece. We will get an answe...

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KYOCERA Programming Contest 2023（AtCoder Beginner Contest 305） Announcement We will hold KYOCERA Programming Contest 2023（AtCoder Beginner Contest 305）. - Contest URL: https://atcoder.jp/contests/abc305 - Start Time: http://www.timeanddate.com/worldclock/fixedtime.html?iso=20230610T2100&p1=248 - Duration: 100 minutes - Number of Tasks: 8 - Writer: MMNMM, [user:Nyaan,2023-06-10], [user:evima,2023-06-10], [user:nok0,2023-06-10] - Tester: [user:PCTprobability,2023-06-10], [user:nok0,2023-06-10] - Rated range: ~ 1999 The point values will be 100-200-300-450-475-525-550-650. We are looking forward to your participation!

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Cities Of CodeForces — 2 Country and city in Codeforces user profiles are often not a the place of the residence but a state of mind. I am sure those 197 users who selected Antarctica as their country feel that their surrounding is cold. Or cool ) The map below shows data from user profiles which have both country and city. So only 16 of all antarctic profiles were taken into consideration, because other have empty city field. On 27 June 2021 there were 351898 users in the rating list. 88752 profiles contained both country and city. There were 4162 unique values of City field for 180 unique values for Country field. The size of circle is proportional to user number and different colors are used to divide cities on groups with the following numbers of users: <20, 20-99, 100 -249, 250-999, >1000.  _._ [cut] _._ But let's look at some closeups.  ...

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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...

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Haskell solutions For those who are interested, here is a list of all problems for which Haskell solutions have been submitted. (Use the 'Status filter' to show only the Haskell submissions.) [1A](http://codeforces.com/problemset/status/1/problem/A) [1B](http://codeforces.com/problemset/status/1/problem/B) [1C](http://codeforces.com/problemset/status/1/problem/C) [2A](http://codeforces.com/problemset/status/2/problem/A) [2B](http://codeforces.com/problemset/status/2/problem/B) [2C](http://codeforces.com/problemset/status/2/problem/C) [3A](http://codeforces.com/problemset/status/3/problem/A) [3B](http://codeforces.com/problemset/status/3/problem/B) [3C](http://codeforces.com/problemset/status/3/problem/C) [3D](http://codeforces.com/problemset/status/3/problem/D) [4A](http://codeforces.com/problemset/status/4/problem/A) [4B](http://codeforces.com/problemset/status/4/problem/B) [4C](http://codeforces.com/problemset/status/4/problem/C) [4D](http://codeforces.com/problemset/status/4/problem/D)...

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Hack me! (Codeforces Round #280 (Div. 2)) Brief stats about some past contest &mdash; [contest:492]. Previous posts can be found [here](http://codeforces.com/search?query=hackme). [cut] <h3>Stats</h3> Problem | <small>Successful hacks</small> | <small>Unsuccessful hacks</small> | Other | Sum | <small>Solutions which can be hacked</small> | <small>Accepted solutions</small> | <small> All solutions on final tests</small>| :---:|:---:|:---:|:---:|:---:|:---:| <small> [problem:492A] </small> | 7 (17.95%) | 28 (71.79%)| 4 (10.26%) | 39 | 104 (3.94%) | 2538 (96.06%) | 2642 | <small> [problem:492B] </small> | 11 (25.00%) | 26 (59.09%)| 7 (15.91%) | 44 | 120 (5.90%) | 1915 (94.10%) | 2035 | <small> [problem:492C] </small> | 149 (48.85%) | 54 (17.70%)| 102 (33.44%) | 305 | 340 (21.55%) | 1238 (78.45%) | 1578 | <small> [problem:492D] </small> | 7 (22.58%) | 18 (58.06%)| 6 (19.35%) | 31 | 138 (23.47%) | 450 (76.53%) | 588 | <small> [problem:492E] </small> | 0 (0.00%) | 1 (100.00%)| 0 (0.00%) | 1 | 5 (2.81%) | 173 (97.19...

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My New Judge in Python More details can be found at [https://github.com/cdqzoi/pjudge/tree/master/src](https://github.com/cdqzoi/pjudge/tree/master/src), bug report and any other suggestions are welcomed :D. My judge creates a virtual root for each test, which has only the executable binary file in it, and the directory is not writable for the program. Here is my code: (you can find it in my github at src/judge.py) ~~~~~ #!/usr/bin/python2.7 import multiprocessing, subprocess, time, os, resource, signal, sys _scale = {'kB': 1024, 'mB': 1048576, 'KB': 1024, 'MB': 1048576} def _compare(usr, std): usr = usr.strip() std = std.strip() std = std.split("\n") usr = usr.split("\n") lstd = len(std) lusr = len(usr) if lstd != lusr : return 0.0 for _ in range(0, max(lstd, lusr)): try: stdl = std[0].strip() del std[0] except IndexError: stdl = '' try: usrl = usr[0].strip() del usr[0] except IndexError: usrl = '' if(stdl != usrl): retu...

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Mapping of SGU Problem IDs to Contests? A lot of, if not all, of the SGU problems come from old contests, though the SGU problem statements themselves often do not have the contest attribution associated with them. For example, problems 542 through 553 are the 2012 NEERC Southern Subregional, but that attribution is not present in the problem statements (as of the time of this post). Compare this with problems 201 through 208, which are stated as being part of a Petrozavodsk training contest (specifically ASC 2, though that is not explicitly mentioned in the statements). I'd like to assemble/crowdsource a comprehensive mapping of SGU problem IDs to the contests where the problems were originally hosted, and additionally links to them in the Codeforces gyms if they're hosted there. Does anyone have this mapping? I'm curious if the admins or anyone familiar with how the SGU problems were sourced to begin with can help out here, otherwise this can be easily crowdsourced. - 193-200: http://codeforces.com/gym/100199 (ASC 1...

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Enumeration of vertex pairs which are connected by a path of infinitesimal weight. <p><span style="font-family: verdana , arial , sans-serif;font-size: 13.0px;text-align: left;background-color: rgb(255,255,255);">Thanks for translation by </span><a class="rated-user user-blue" href="http://codeforces.com/profile/RodionGork" style="font-family: arial;text-decoration: none;font-weight: bold;color: rgb(0,0,204);font-size: 11.0px;text-align: center;background-color: rgb(248,248,248);" title="Expert RodionGork">RodionGork</a></p><p><span style="font-family: verdana , arial , sans-serif;font-size: 13.0px;text-align: left;background-color: rgb(255,255,255);">Problem statement:</span><br style="font-family: verdana , arial , sans-serif;font-size: 13.0px;text-align: left;background-color: rgb(255,255,255);" /><span style="font-family: verdana , arial , sans-serif;font-size: 13.0px;text-align: left;background-color: rgb(255,255,255);">Given an oriented graph with N vertices and M edges we are to find all vertex pairs for which exists a path of infinitesimal weight.</span> <br /...

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A week with a new max-flow problem [http://petr-mitrichev.blogspot.com/2015/06/codeforces-round-305-started-this-weeks.html](http://petr-mitrichev.blogspot.com/2015/06/codeforces-round-305-started-this-weeks.html)

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No problem solved, no hack : became Master with +209 This is the first time I write blog. Here's my story... While I was looking at rating changes in Round 305 div 1 http://codeforces.com/contest/547/ratings , I've noticed contestant [user:sheisactually14,2015-06-04] who gained +209 but took place 631. I looked carefully in his profile and found something strange. His contests tab : http://codeforces.com/contests/with/sheisactually14 If you click to the number 177, his place, you will see : http://codeforces.com/contest/547/standings/participant/4756047#p4756047  He gained +209, became Master but solved no problems and had no hacks. Can someone, I wish [user:MikeMirzayanov,2015-06-04], explain for me about this magic ? Or is there a bug in rating system ? Oh hell... What a myth actually !

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C. Anya and Ghosts: Wrong answer in test 61 please help I can not understand why my code make wrong answer for the last test. my algorithm is same as editorial and my code is like some others that I have seen. The question is [problem:508C]. the C problem of last contest. and my code: [submission:9606896 ] int m, t, r; int wr[305]; bool can[611]; int num[611]; int res = 0; int main() { cin >> m >> t >> r; For(i, 0, m) { cin >> wr[i]; wr[i] += 304; } int now, need, j; if (t >= r) { For(i, 0, m) { now = wr[i]; need = r - num[now]; for (int l = 1; l <= t; l++) { if (need <= 0) break; j = now &mdash; l; if (can[j] != true) { can[j] = true; res++; need--; For(k, 0, t) { num[j + 1 + k]++; } } } if (need > 0) { cout << -1 << '\n'; return 0; } } cout << res << '\n'; return 0; } cout << -1 << '\n'; return 0; }

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Codeforces Global Rounds 2021: Final Results (GR13-GR18) Tomorrow will be the first global round of this year. And we are happy to sum up the results of last season. We announce the results! We remind you that the global rounds are a joint initiative of XTX and Codeforces. We are happy to announce that they continue into the new year. We hold 6 such rounds per year. All of them are open to both divisions. At each such round, 50 brand T-shirts were handed out, and we are happy to give T-shirts to all problem authors. The prizes for the 6-round series are: - 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. The final standings after six rounds (sorted by total points in four best placed rounds): | Place | Contestant | = | GR 13 | GR 14 | GR 15 | GR 16 | GR 17 | GR 18| |--...

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IOI 2023 Country Standings Hello everyone! Similar to [last year](https://codeforces.com/blog/entry/105957), these are the country standings for IOI 2023 based on the sum of scores of all contestants. Check the spoiler at the bottom for the complete list. <table style="width:100%"> <tr> <th>Rank</th> <th>Team</th> <th>Score</th> </tr> <tr> <td>1</td><td>CHN</td><td>1997.5</td></tr> <tr> <td>2</td><td>USA</td><td>1624.5</td></tr> <tr> <td>3</td><td>JPN</td><td>1574</td></tr> <tr> <td>4</td><td>IOI_2</td><td>1463.5</td></tr> <tr> <td>5</td><td>TWN</td><td>1296</td></tr> <tr> <td>6</td><td>KOR</td><td>1218.5</td></tr> <tr> <td>7</td><td>POL</td><td>1201.5</td></tr> <tr> <td>8</td><td>ISR</td><td>1187.5</td></tr> <tr> <td>9</td><td>CAN</td><td>1168</td></tr> <tr> <td>10</td><td>VNM</td><td>1129.5</td></tr> </table> <spoiler summary="Complete list"> <table style="width:100%"> <tr> <th>Rank</th> <th>Team</th> <th>Score</th> </tr> <tr> <td>1</td><td>CHN</td>...

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Codeforces Global Rounds 2021: Current Results (GR13-GR17) In 2021 (as in 2019 and 2020), with the support of XTX Markets, 6 rounds of the new Codeforces Global Rounds are held: common rounds for both divisions of 7–9 problems each. The duration of the rounds is 2-3 hours, depending on the number and complexity of the problems. All such rounds are rated for all participants. <i>At each such round, 50 brand T-shirts are handed out, and we are happy to give T-shirts to all problem authors.</i> The prizes for the 6-round series in 2021: - 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 five rounds he placed the highest. - The best 20 participants over all series get sweatshirts and place certificates. Current standings after five rounds (sorted by total points in four best placed rounds): | Place | Contestant | = | GR 13 | GR 14 | GR 15 | GR 16 | GR 17| | - | - | - | - | - | - | - | - | | ...

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The entire cses problem set sorted by the number of solvers! I could not find it online so I made it myself, I hope you will find it useful! Problem : Number of solvers - Weird Algorithm : 73338 - Missing Number : 62177 - Repetitions : 54281 - Increasing Array : 50436 - Permutations : 44614 - Distinct Numbers : 33154 - Dice Combinations : 32886 - Number Spiral : 31522 - Bit Strings : 29957 - Minimizing Coins : 28281 - Trailing Zeros : 28124 - Coin Combinations I : 26104 - Two Sets : 25446 - Coin Piles : 24696 - Apartments : 24318 - Removing Digits : 24291 - Two Knights : 23643 - Grid Paths : 23168 - Ferris Wheel : 23109 - Counting Rooms : 22561 - Palindrome Reorder : 22339 - Coin Combinations II : 22133 - Sum of Two Values : 21004 - Maximum Subarray Sum : 20797 - Book Shop : 20376 - Creating Strings : 19359 - Building Roads : 19197 - Restaurant Customers : 18982 - Concert Tickets : 18507 - Apple Division : 18503 - Stick Lengths : 18339 - Movie Festival : 17839 - Message Route : 16337 - Building Teams : 1578...

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Calculating Combinations Hello CF community, I'm trying to solve this [problem](https://onlinejudge.org/index.php?option=onlinejudge&page=show_problem&problem=305), the problem tells me that I have to calculate $$C_n^r = \frac{N!}{M!\cdot (N-M)!}; 5\leq N\leq 100, M\leq N$$ in the numerator it will always be $\prod _{i = N-M+1}^{n} i$ and in the denominator will be $ \prod _{i=1}^{min(N, N-M)}i$ as the rest will cancel out and this is my code:  **but it gives me WA, I'm not really sure why I'm getting this. Any ideas?**

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Проверка переполнения Всем привет.<br> На [contest:305] моё решение взломали из-за переполнения во время умножения. В связи с эти вопрос. Если есть две переменные типа int64, то как проверить, происходит ли переполнение при вычислении a*b?

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305 Div.1 C Hi, I'm having a hard time understanding the author's solution for [this problem](http://codeforces.com/contest/547/problem/C) . I would appreciate it if anyone could explain his/her accepted solution. Thank you in advance.

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Codeforces Global Rounds 2022: Final Results (GR19-GR24) Hello, Codeforces. It's time to take stock of last year. Shall we begin? And we are happy to sum up the results of the last season of Global Rounds. We announce the results! We remind you that the global rounds are a joint initiative of XTX and Codeforces. We hold 6 such rounds per year. All of them are open to both divisions. At each such round, 50 brand T-shirts were handed out, and we are happy to give T-shirts to all problem authors. The prizes for the 6-round series are: - 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. [cut] The final standings after six rounds (sorted by total points in four best-placed rounds): | Place | Contestant | = | GR 19 | GR 20 | GR 21 | GR 22 | GR 23 | GR 24| |--|--|--|--|...

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WRONG ANSWER IN TESTCASE IN #CODEFORCES ROUND 305 I tried to solve #codeforces round 305 div2 problem B nnamed mike and fun. when i submitted the solutions it is showing wrong answer for the testcase #4 .the first line of output should be 4 but it is showing 3 . so what can be the possible reason for this error ? please post here.

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First Ever Users to Reach Some Rating Milestones Revised: ratings below 1500 and greatest rises Several days ago I published a [table](https://codeforces.com/blog/entry/104320) with first people to reach certain ratings. It featured only ratings above 1500, and [user:adamant,2022-07-09] advised to do the same, but on achieving ratings below 1500. I found it quite interesting, and, after several days of collecting data about participations of 447911 Codeforces users, I finally made this table. [cut] For several reasons I firstly put another table. This is the table of greatest rating rises in the history of Codeforces. The reasons are: 1. I have collected so much data from Codeforces that it would be blasphemy not to use it in as many ways as possible. 2. These tables might intersect a lot: it's easier to get a terrific rise in ratings if you are low-rated. (Many people abuse this and deliberately get very low-rated to make a great jump.) 3. Someone recently posted a table with greatest rating rises and falls. I wasn't able to find this table to check whether it was...

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