Hello, Codeforces.

We live in difficult times. And, unfortunately, our community is highly dependent on world events around us. Three years ago, it seemed easy to send a t-shirt anywhere in the world. Now it's a quest with many unknowns. Just a few months ago, it was not difficult to send a reward to the problem writer. But now, we are cut off from the outside world and regulated by multiple new laws.

And here it is very important not to lose, not to break what has already been done. Don't stand still, move forward. I am very glad and grateful to the problem writers and coordinators that in March we managed to hold 10 ratings (we held 9, come to participate in the tenth). Thanks to everyone who took part in the preparation!

And I want to share another great news. Our friends NEAR has come up with the initiative to support the community during this difficult time. We are pleased to announce that the upcoming rounds will be funded by NEAR, which will help with the payment of rewards to problem writers and coordinators. This is a timely and important help. Thanks!

It will be easier and faster for us if the problem writers or coordinators have the opportunity to accept a reward in the form of a cryptocurrency transfer. In this case, we are ready to transfer 25% more and make the transfer much faster. Oh, it's a pity we can't send t-shirts with crypto.

And I remind you that the next round (and Codeforces Round #780 (Div. 3)) is waiting for you) will take place very soon, on Mar/31/2022 17:35 (Moscow time). I hope to see you among the participants.

— Mike

TLTR: If you are in the top-1000 of CodeTON Round 1, then fill out the form by the link https://codeforces.com/userForm/203c74605996e40f. Also, anyone who solved at least one problem in the round can fill out it and get 1 TON airdrop. The deadline is 23:59:59 (UTC +3) 04.04.22.

Hello. Great news from the TON Team. I give them the floor.

Good news everyone!

We decided to celebrate the successful finish of the CodeTON round by airdropping all the people who have solved at least one of the problems (officially, practice and virtual participation don't count) of the CodeTON round. Such participants are eligible for 1 TON airdrop and a memorable NFT. Please do note that such NFT bears only symbolic value and is not entered to have any financial or investment value.

Please submit your TON wallet address via the link https://codeforces.com/userForm/203c74605996e40f if you are eligible for such an airdrop by 23:59:59 (UTC +3) 04.04.22.

Winners are more than welcome to provide organizers with the TON Wallet addresses to claim their prizes.

We also want to invite all of you to try yourself at TON Smart Challenge contest aimed at contract source code optimization: https://t.me/toncontests/26

You can read more about this competition here:

Thank you for taking your part, hope you enjoyed the round, looking forward to meeting you later!

TON Foundation

Xin chào, Codeforces! (Hello, Codeforces!) ٩ (◕‿◕｡) ۶

Me, _FireGhost_ and SPyofgame are glad to invite you to Codeforces Round 779 (Div. 2), which will take place on Mar/27/2022 17:35 (Moscow time). The round will be rated for participants with rating lower than 2100. You will have 2 hours to solve 6 problems, one of which is divided into two subtasks.

In this contest, you will meet Kitagawa Marin and her friends Gojou, Juju and Shinju from My Dress-up Darling! We hope you will find our problems interesting. Good luck to you all! (ﾉ ◕ ヮ ◕) ﾉ *: ･ ﾟ ✧

We sincerely thank the following people for their contributions in the round:

• errorgorn for rejecting 20 problems from SPyofgame coordinating the round and KAN who guided him in his first coordination.

• SPyofgame and myself for setting problems and _FireGhost_, mewnian, _LEOS_, Mondeus for helping us prepare problems.

• antontrygubO_o for providing the idea for one of the problems.

• Kuroni for being the problemsetter team's caretaker the English proofreader.

• _FireGhost_, mewnian, _LEOS_ and SuckTinHock for setting tasks which failed to make the final problemset.

• Monarchuwu for breathing and SPyofgame for being the team's punching sandbag.

• antontrygubO_o, Kuroni, thenymphsofdelphi, darkkcyan, rama_pang, Yurushia, ngpin04, hieplpvip, Pichu, maomao90, FallingStar, Mike4235, Lyde, BaoJiaoPisu, HynDuf, NguyenDangQuan, thanhchauns2, vodacbaoan, hieu_2004, novaland, DMCS, Dirii, welleyth, QuangBuiCPP, Minhho2005, Kriz_Wu, sweet_hope25, kieusontungcva, CrazyDave53, KarD1m, damnson, lk2147, 2qb, OnionEgg for testing the round and providing useful feedback.

• unreal.eugene, geranazavr555 and MikeMirzayanov for Russian translations.

• MikeMirzayanov for great Codeforces and Polygon platforms.

Score distribution: $$$500-1000-1750-(1250+750)-2500-3000$$$

UPD: Editorial

Congrats to the winners:

1. tourist
2. disorientation
3. A-SOUL_Official
4. Geothermal
5. oleh1421

Hello!

It is a pleasure to invite you to CodeTON Round 1 (Div. 1 + Div. 2, Rated, Prizes!)! The round will take place on Mar/24/2022 17:35 (Moscow time). The round will be rated for all participants. The problems of the round were authored by FelixMP, and they were prepared by FelixMP and xpov1LL.

I would like to thank the following people:

• Baqtraqking for having the idea of preparing a Codeforces Round and helping with the solution to one problem; Baqtraqking, izanbf and xpov1LL for early help and discussion of problems, and Baqtraqking, xpov1LL and OneStone for proposals that did not make it to the final problem set.
• 74TrAkToR for coordination of the round.
• MikeMirzayanov for the great platforms Codeforces and Polygon.
• Um_nik, Monogon, AlexLuchianov, generic_placeholder_name, TeaTime, EdgarMM19, cescmentation_folch, metatron, plagues, mathusalen, javierlc2000, DIvanCode, Farrius for testing the round and providing feedback.

There will be 9 problems in the round, with score distribution $$$500 - 1000 - 1500 - 2000 - 2500 - 3000 - 3250 - 3750 - 4500$$$. Hope you have fun!

UPDATE: Editorial.

Here is information from our partners:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support the CodeTON round and invite you to the TON Smart Challenge 1 competition, which will be held on our platform.

The Open Network (TON) is a fully decentralized blockchain created by the Telegram team for a mass audience.

The TON protocol was designed by Nikolai Durov — who is a two-time ICPC world champion, a three-time IMO gold medalist, a multiple IOI medalist, and a co-founder of Telegram — and other winners of international competitions. Now TON is being developed by a community of independent developers and teams.

The winners of CodeTON Round 1 will receive valuable prizes.

The first 1,000 participants will receive prizes in TON cryptocurrency:

• 1st place: 1,000 TON
• 2–3 places: 600 TON each
• 4–10 places: 100 TON each
• 11–100 places: 15 TON each
• 101–1,000 places: 8 TON each

Also, the top 15 participants of CodeTON Round 1 will receive branded hoodies.

In addition, a separate TON Smart Challenge 1 contest will start on our platform on March 28. We invite you to join this competition as well.

You can read more about this competition here:

We believe that the problems of optimizing the efficiency of smart contract code execution on the TON blockchain may be of interest to participants in algorithmic competitions. The development of smart contracts is a case where the experience of optimization earns money by definition because a network fee is paid for each operation on the blockchain.

We wish you good luck at CodeTON Round 1 and hope to see you among the TON Smart Challenge participants!

UPD: If you have got into prizes or just want to join the TON, then register a wallet, follow one of these links: https://tonkeeper.com/ or https://wallet.ton.org/

Hello Codeforces!

On Mar/22/2022 17:45 (Moscow time) Educational Codeforces Round 125 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

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 adedalic Dalabaev, Vladimir vovuh Petrov, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

UPD: Editorial is out.

Hi everyone!

The Final Round of Technocup 2022 starts this Sunday, March 20, 2022 at 11:00 MSK (09:00 UTC)!

The final results of the Technocup Final Round >>>

For those who want to compete on the same problems, we will hold a regular Codeforces Round, combined for both divisions. The round is starting at Mar/20/2022 14:35 (Moscow time).

If you are a participant of the official Technocup Finals, you are not allowed to take part in the round 778. We ask participants of the official Finals not to discuss the problems in open media till evening.

This round is possible thanks to the following people:

• TheScrasse and myself for inventing and preparing the problems.
• dario2994 for coordinating the round (and Um_nik who helped him by giving his opinion on the problem set, and KAN who guided him in his first coordination).
• cry, US3RN4M3, angeredgecko, franfill, lorenzoferrari, NemanjaSo2005, TeaTime, manish.17, Logic_zys, kpw29, generic_placeholder_name, irkstepanov, KAN and gamegame for testing the round.
• MikeMirzayanov for creating Codeforces and Polygon.

Score distribution: $$$500 - 750 - 1250 - 2000 - 2500 - 3000 - 3500 - 4000$$$

UPDATE: Editorial is out

UPDATE: Congratulations to the winners:

1. Golovanov399
2. orzdevinwang
3. Rewinding
4. xtqqwq
5. ugly2333

Hello!

The most problems on Codeforces are "classic input-output" problems in which you have to write an entire program: read the input and write the answer. Also, there are "interactive" problems in which you have to interact with a jury's program. But Codeforces supports some other types of problems: problems with graders and output-only problems.

You can test an output-only problem and a problem with grader in this mashup.

Problems with graders

In such problems, you (a participant) have to implement not the entire program but only some interface or function described in the problem's statement. For example. you may be asked to implement function f(a: int, b: int, c: int) -> int in Python or int f(int a, int b, int c) in C++. Only Python and C++ are supported for now for such problems.

For problem writers: read this post and this post to learn how to create a problem with a grader. The example problem with a grader is already shared with all Polygon users.

Output-only problems

In such problems, you (participant) have to send only a zip-file with outputs on each test (or only on a subset of tests). The structure of the zip file must be following:

archive-name.zip
|
|- 01.out
|
|- 02.out
|
|- 03.out
...

I.e. zip-file must contain text files with the outputs named like <2-digits-test-index>.out.

Commonly, each problem could be marked as output-only, but it's recommended to publish tests using the "Problem materials" section in Polygon (see this post to learn more).

Привки, Кодефорсес (ﾉ◕ヮ◕)ﾉ*:･ﾟ✧

(Hello, Codeforces on Russian)

Igorbunov and I are happy to invite you to participate in Codeforces Round 777 (Div. 2), all the tasks of which will be about a little girl Madoka. It will take place on Mar/11/2022 17:35 (Moscow time). The round will be rated for all participants with rating strictly lower than 2100. You will have 2 hours to solve 6 problems.

I would also like to express my gratitude to the following people:

• To our cute coordinator Artyom123.
• To cute testers for cute feedback on cute tasks: FelixDzerzhinsky, lesssia, eyakm1, _Vanilla_, morzer, welleyth, TeaTime, Dart-Xeyter, Kon567889, Renedyn, Pechalka, talant, Ziware, vaaven, princebelkovetz, Alexdat2000, crazyilian, antontrygubO_o, generic_placeholder_name.
• MikeMirzayanov you know why.
• To our dear mothers.
• purplesyringa for a verification english statements.

I wish you high rating, and I also hope that I will help you to distract from bad news at least a little ( ❤ ω ❤ )

Scoring distribution: 500 — 1250 — 1500 — 2000 —2500 — 3000

UPD1: Editorial

UPD2: Congratulations to the contest winners

Div 1+2

Div 2

Hello Codeforces!

On Mar/10/2022 17:35 (Moscow time) Educational Codeforces Round 124 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

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 adedalic Dalabaev, Vladimir vovuh Petrov, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

UPD: Editorial is out