The contest is over; I hope you've enjoyed it :-) Editorial is here.

The 6th April Fools Day Contest will take place on Sunday April 1st. 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, 2013, 2014, 2016, 2017.

As usual, to enjoy competing in this round you'll need a sense of humor compatible with mine! Good luck, and have fun!

Hi!

Tomorrow, on March 24-th, 2018 at 15:35 UTC we will host the second round of VK Cup 2018 — a programming tournament for Russian-speaking youth. 450 teams that were the best in the first round and the first wild-card round will compete tomorrow. The top 100 teams will advance to the third round directly and get a tournament t-shirt, while the others will have one more chance in the second wild-card round.

For English-speaking community as well as for those who haven't advanced to the second round or haven't participated in VK Cup 2018, we will host parallel Codeforces round for both divisions, as usual. Feel free to take part!

Please note that the tournament is for Russian-speaking people. If you don't speak Russian, you must not compete in the VK Cup round, register for the parallel round instead. Otherwise it is considered as a flagrant violation of rules and might be subject to disqualification and Codeforces ban. Please respect the organizers.

VK Cup 2018 Round 2 and the round for the first division will have six problems each, the second division round will have five of them.

The authors of the problems are cyand1317, skywalkert, Claris and me. Also many thanks to fcspartakm, Tommyr7 for their help in preparation and PavelKunyavskiy, winger, AlexFetisov, Errichto, vepifanov, immortalCO and qwerty787788 for testing the problems! Last but not least, huge thanks to vintage_Vlad_Makeev for his great help in coordinating and testing the round!

Good luck!

The editorial is published!

Congratulations to the winners!

VK Cup Round 2:

1. LHiC, V--o_o--V — solved all problems!
2. egor_bb, Nikitosh
3. -imc-, Golovanov399
4. AllCatsAreBeautiful, arsijo
5. aid

Div. 1:

1. Um_nik
2. Radewoosh
3. ikatanic
4. FizzyDavid
5. jqdai0815

Div. 2:

1. ltf0501
2. Hyperbolic
3. yongshiboshi
4. emengdeath
5. lmhoang

Less than 24 hours till the round?
And still no announcement?
How come, Mr. Grape?

Codeforces Round #471 will take part on Friday at 19:35 MSK. Note that the duration is a bit longer that usual.

The round will be rated for all division 2 participants. Division 1 is welcome aswell :)

My gratitude to Grisha (vintage_Vlad_Makeev) for round coordination, Ildar (300iq), Nikita (FalseMirror), Azat (ismagilov.code), Eugene (rek) and Oleg (xen) for testing and Mike (MikeMirzayanov) for awesome Codeforces and Polygon.

There will be six problems with the following scoring:
500 — 1000 — 1500 — 2000 — 2500 — 3000

UPD. System testing is over. Editorial

Congratz to the winners!

Div. 2:

1. 08163268
2. heello
3. KNB.
4. flower
5. NotGuy
6. HarveySpecterGoiano
7. seo
8. JorreS
9. zhabo
10. Osama_Alkhodairy

Div. 1 (unofficial):

1. uwi
2. Taube
3. dreamoon_love_AA
4. mjhun
5. chemthan
6. Hasan0540
7. tfg
8. cerberus97
9. mixnuts
10. Lo_R_D

Hello Codeforces!

On March 22, 9:05 MSK Educational Codeforces Round 40 will start. This will be a special round, branded by VTB and the Hello India x Russia Programming Bootcamp.

This round is held in collaboration with Hello India x Russia Programming Bootcamp and supported by the premier and international bank VTB, based in Russia.

Over 100 participants from the India side of the boot camp will be competing as individuals in this special online round!

JSC VTB Bank was founded in 1990, and its subsidiary banks and financial organisations (VTB Group or the Group) are a leading Russian financial group, offering a wide range of financial and banking services and products in Russia, the CIS, and a number of countries in Europe, North America, Asia, and Africa. VTB Group has the most extensive international network among all Russian banks, including more than 30 banks and financial companies in more than 20 countries.

The round will contain 9 problems, and you will have 3 hours to solve them. Problem authors are GlebsHP, vovuh, awoo, Xahandd and me.

We wish all of the participants good luck! Hope all of you will find something interesting in this contest.

UPD: Editorial is here.

Congratulations to the winners:

Congratulations to the best hackers:

And finally people who were the first to solve each problem:

Hi!

Tomorrow, on March 17th, 2018, at 15:35 UTC 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: fcspartakm, MikeMirzayanov and me. Thanks to vovuh, GreenGrape, FalseMirror, Glebodin and vintage_Vlad_Makeev 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 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 rounds. After that we will add all succesful hacks and our tests and rejudge all submissions. Then the results will be final.

The main difference between ACM ICPC rules and this round is the following rule.

You should submit each problem in a unique programming language. Different compilers of same language are considered the same language. For example, GNU G++, GNU G++ 11, GNU G++ 14 and MS C++ compilers are C++ language. Thus, you are not only to solve problems, but also try different and new for you languages. We don't think you know 10 languages, we hope that you will quickly learn some basic syntax.

Formally, the following check is performed when you submit a task:

• If there is at least one submission in queue or submission that passed at least one test for this problem in another language, your solution will be ignored. Thus, if your program passes at least one test, you can only solve this problem using this language.
• If there is at least one submission in queue or submission that passed at least one test for another problem in same language, your solution will be ignored. Thus, you can't use a language for more than one problem.

Remember that you can view filter status of some other round by language and view submissions in a specific language. Also, you can view examples of codes in any of the supported languages on the table below. Also, the table contains the groups of compilers considered the same language.

You can use "custom invocation" tab to run a solution if you don't have the compiler locally.

The main rules of ACM ICPC contest: each problem can either be completely solved (when all tests are passed), or not solved. The participants are ranked by the number of solved problems, in decreasing order, in case of a tie they are ranked by penalty time. The penalty time is the sum among all problems the time in minutes that had passed between the start of the round and the moment the problem got solved, plus 20 minutes for every rejected submission. Note that the problems are not arranged by difficulty. Also, you can resubmit a solution even if it passed all tests, because there will be more tests after the open hacks.

Good luck!

Hello everyone! Today, on March 13 at 9pm MSK the second qualification round of Yandex.Algorithm 2018 tournament will take place. You can get to the contest page from the Algorithm site.

The problems are by me, Mikhail Tikhomirov. I am grateful to Gleb GlebsHP Evstropov for his help with problems preparation, and also ifsmirnov, halyavin, kuzmichev_dima, scorpion for testing the problems.

Good luck, see you at the competition!

The round 1 of VK Cup 2018 will take place on March 10 at 18:35 MSK (check your timezone). The contest "VK Cup 2018 — Round 1" is for teams qualified from two Qualification Rounds. The top 400 teams will advance to the Round 2, along with teams that qualify in the Wild Card Round 1 a week later. As usual, there will be two parallel rounds for those ineligible to participate in VK Cup, one for each division.

I'd like to thank KAN for steering my crazy ideas into a coherent unit, the coordination and also for suggesting one of the problems, AlexFetisov, qwerty787788, winger, Errichto, Tommyr7 and misof for testing the problems, MikeMirzayanov for building Codeforces and Polygon and VK for organising the contest.

All three rounds last 2 hours, and all are rated. The VK Cup and Div. 1 will have six identical problems while the Div. 2 contest will consist of five problems. The scoring distribution will be announced before the contest.

The main heroes of this round will be Alice and Bob. Beware that Eve might attempt to foil their plans.

This is my first round on Codeforces and hopefully not the last. Wish you many submissions, high hacks and successful rating.

UPDATE: The scoring in Div.1 and VK Cup round 1 is 500-1000-1500-1750-2250-3000. For Div.2, it is 500-1000-1500-2000-2250.

UPDATE2: The round is finished. I hope you enjoyed it. Tune in a bit later for editorial.

UPDATE3: Congratulations to winners!

Div.1

• Memphis
• Um_nik
• enot110
• Deemo
• krijgertje

Div.2

• queryquerynk
• siiri
• NBAH
• pupiI
• fake123

VK Cup

• Perforator, BledDest
• Andrew_Makar, BigBag
• fdoer, Skird
• SmallBoy, Na2a
• AllCatsAreBeautiful, arsijo

UPDATE4: Editorial

Hi all.

I want to introduce you a small game I made about codeforces.

It is web game. Here is the link: https://craus.github.io/codeforces-simulator/

Also created a "More games" section there, if you would be interested in my other games. I love making them. One was released on Steam yesterday. You can сheck it out as well.

Hi everybody,

Today there will be the first day of Moscow Open Olympid, that is the personal programming competition that is held in Moscow each spring. This contest is prepared by Moscow Olympiad Scientific Committee that you may know by Moscow Team Olympiad, Moscow Olympiad for Young Students and Megapolises Olympiad (rounds 327, 342, 345, 376, 401, 433, 441, 466).

Open Olympiad consists of the most interesting and hard problems that are proposed my a wide community of authors, and that is why we decided to give you an opportunity to crack the complete problemset of the contest by making some kind of an experiment. Tomorrow we are going to conduct a rated Codeforces round based on problems of both days of our Olympiad.

We kindly ask all the community members that are going to participate in the competition to show sportsmanship by not trying to cheat in any manner, in particular, by trying to figure out problem statements from the onsite participants. If you end up knowing some of the problems of Moscow Open Olympiad (by participating in it, from some of the onsite contestants or in any other way), please do not participate in the round. We also ask onsite contestants to not discuss problems in public. Failure to comply with any of the rules above may result in a disqualification.

Round will happen at 11:05, March 9th, Moscow time and will last for 2.5 hours. There will be 6 problems in each division.

Round problems were prepared by ch_egor, Sender, Flyrise, cdkrot, malcolm, vintage_Vlad_Makeev under supervision of your humble servant with a great help of meshanya, GlebsHP, Endagorion and Helen Andreeva. Some of the div2 problems were finalized with help of Codeforces team represented by fcspartakm, also we would like to thank round coordinator KAN for his help in deciding which problems to take and all the discussions.

Good luck everybody!

UPD: Announcement email contained incorrect start time. Instead of "12:05, March 9th, Moscow time, 2 hours" it should be "11:05, March 9th, Moscow time, 2.5 hours", as was originally in the round announcement.

UPD2: Round is postponed by 10 5 minutes. Stay tuned :)

Congratulations to the winners!

Division 1:

1. dotorya
2. Swistakk
3. Syloviaely
4. zscoder
5. dreamoon_love_AA
6. SkyDec
7. Marcin_smu
8. yutaka1999
9. Kostroma
10. Will_Dearborn

Division 2:

1. _ChenKerui
2. Demerzel_IV
3. 879333752
4. yyc_jm
5. Anson529
6. iotang
7. wcz112
8. Hankpipi
9. cyz666
10. wwd2075

UPD3: Finally, the editorial is there! Kudos to vintage_Vlad_Makeev and ch_egor for making it appear in a text form.