Hi Codeforces!

On Dec/03/2024 09:25 (Moscow time) we will hold Codeforces Round 990 (Div. 1) and Codeforces Round 990 (Div. 2). Note the unusual starting time!

The harder problems of this round are based on the problems from the Final round of Yandex Cup 2024, Algorithms track, that will be held at the same time.

The problems are authored by elshiko, Flyce, MrLolthe1st, sokolow, stepanov.aa, TeaTime, Tikhon228, webmonster, 4qqqq with guest problems from myst-6, Vladithur, BledDest and me.

I'd like to thank daubi, Golovanov399, arbuzick, pperm, orz, AgafonovArtem, Qwerty1232, k1r1t0, Itsmylove1, Sofi_, and errorgorn for testing the problems, tourist for helping with the round, and MikeMirzayanov for the Polygon and Codeforces systems.

Because of official Yandex Cup Finals ends later than the round on Codeforces, the upsolving, solutions, and test cases will be closed until the end of the onsite contest, roughly 3 hours after the end of the Codeforces round. It is also forbidden to discuss the problems publicly until the end of the onsite round. Any comments here concerning the problems will be removed.

Good luck!

UPD: The contest has been delayed to make sure the online contest does not start earlier than the onsite one.

Congratulations to the winners!

Div. 1:

1. jiangly
2. hank55663
3. noimi
4. cxm1024
5. Pyqe

Div. 2:

1. RGB_ICPC8
2. timer2024
3. tietieAM
4. ylzxxx7
5. mion_sonozaki

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Neapolis University Pafos. They offer a BSc in Computer Science and AI with JetBrains Scholarships. Gain cutting-edge skills in AI and machine learning, preparing you for high-demand tech careers. Curious? Check out the CSAI curriculum now. Limited scholarships available — don't miss your chance to study in Europe for free!

On Dec/02/2024 17:35 (Moscow time) Educational Codeforces Round 172 (Rated for Div. 2) 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 adedalic Dalabaev, 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!

Selamat pagi Codeforces!

We're going to hold The 2024 ICPC Asia Jakarta Regional Contest.

We invite you to join the online mirror contest 2024-2025 ICPC, Asia Jakarta Regional Contest (Online Mirror, Unrated, ICPC Rules, Teams Preferred) on Codeforces. It'll be held on Dec/01/2024 08:05 (Moscow time) 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 2024 ICPC Asia Jakarta homepage
• The regional information in ICPC Global
• The onsite scoreboard

We hope that you'll enjoy the contest. Good luck and have fun!

UPD. The mirror has ended! You can find the editorial here. The onsite scoreboard will be unfrozen after the closing ceremony. Thank you for participating and we hope that you enjoyed the problemset!

UPD2. Mistake in Problem D. Aquatic Dragon

The act of activating a shrine is supposed to be mandatory once you reach an island instead of being optional. During contest preparation, the initial problem had a statement that implies the aforementioned obligation of shrine activation, which the judges had a correct solution for (the one in the editorial). However, when rewriting the problem statement for more clarity with adjustments to the story, we ended up making it such that it's optional, without too much thought about it, thinking it's essentially still the same problem. Unfortunately, as we have recently found out after the contest, it's in fact not the same problem.

The action we're taking now is fixing the statement of the problem after the contest with the correct intended version without changing the judges' solution. We are very sorry for the inconvenience.

👋 Salam, Codeforces!

We are thrilled to invite you to the Rayan Programming Contest 2024 - Selection (Codeforces Round 989, Div. 1 + Div. 2).

The Selection Round is a rated contest for Div. 1 + Div. 2, taking place on Nov/30/2024 17:35 (Moscow time). The problems for this round were crafted and prepared by ArshiaDadras, MohammadParsaElahimanesh, AmShZ, AmirrzwM, and Keshi.

The top 60 trusted participants (with a maximum of three from each country) will qualify for the onsite Final Round in Tehran, in Spring 2025. An additional quota is reserved for the host country. Hotel accommodation, local transportation, and meals will be provided to all finalists. More details about the final contest will be available on the Rayan website.

🏆 Selection Round Prizes:

• The top 50 participants will receive T-shirts. 👕
• Additionally, 50 random participants from ranks 51-1000 will also receive T-shirts.

🏅 Final Round Prizes:

• 1st place: $15,000 💵
• 2nd place: $10,000 💵
• 3rd place: $5,000 💵
• 4th–6th places: $2,000 each
• 7th–10th places: $1,000 each

🙏 Special Thanks:

We would like to extend our deepest gratitude to:

• MikeMirzayanov for enabling this event through the amazing Codeforces platform.
• The one and only KAN for his invaluable support in hosting the round.
• Dear TheScrasse for his dedicated coordination efforts and lots of discussions about the problems and rejecting a big chunk of our problems for Problem C. He also contributed some problems to the contest, one of which was selected by the team!
• Our testers who tested and provided invaluable feedback to improve the problems: peti1234 for being our LGM (VIP) tester, wyrqwq for his great ideas and ignoring his school midterms to test the problems, Error_Yuan for helping us and picking on tough problems for no reason, Hyperbolic, DylanSmith, valeriu, Clan328, powervic08, CepryH9, mispertion20, PineapplesOnPizza, vyshniak.n, ErrorAssassin, nicolasalba, naniim, estoy-re-sebado, mika_uwu, rulerofcakes, AkiLotus, Random_3652, sleepwalking643, Leonardo_Paes, RockSnow, waidenf, and newb_programmer.
• Prof. Hamid Zarrabi Zadeh and Prof. Mohammad Ali Abam, whose leadership and organizational efforts make this event a reality. Thanks to their vision, Rayan is becoming one of the largest competitive programming contests in terms of prizes (and soon participants!).
• You for participating and getting positive delta (and maybe the final prize in the next year 💸😉).

📊 Score distribution: $$$500 - 750 - 1500 - 1500 - 2000 - (2000 + 2000) - (3000 + 3000) - 5000$$$

We look forward to seeing you both online and onsite!

Good Luck & Have Fun! 🎉

Note: Editorial just published here! 🚀🍿

Hello Codeforces!

I am pleased to invite you to participate in 2024 ICPC Asia Taichung Regional Contest (Unrated, Online Mirror, ICPC Rules, Preferably Teams), which will be held on Nov/24/2024 10:05 (Moscow time). This is an online mirror contest for the 2024 ICPC Asia Taichung Regional Contest, and the official offline contest was conducted on November 17th, 2024. The duration of the contest will be 5 hours and the contest is best for teams of three people. The mirror will use the ICPC format.

The contest tasks are proposed by the task authors (baluteshih, waynetuinfor, skylinebaby,samsam2310, hank55663, ltf0501, Jeffrey, Shik, tmt514, Bangye Wu, kasuistry, and Peter Rossmanith), prepared and polished by the judge team (Regional Contest Director Ling-Ju Hung, Chief Judge Peter Rossmanith, kasuistry, Hung-Lung Wang, baluteshih, waynetuinfor, hank55663, cthbst, Sylveon, CindyLinz, marmot0814, tmt514), and tested by the tester team (olmrgcsi, oToToT, jeeeerrrpop, nikilrselvam, Vince729, applepi216). The judges appreciate the testers for their valuable feedback!

We would like to thank MikeMirzayanov for creating the greatest Codeforces platform, and many, many, many helps for making this online mirror contest possible!

This is a photo of the contest venue. Photo Credit: Prof. Jinn-Shyong Yang.

On behalf of the 2024 ICPC Asia Taichung Regional Contest Judge Team, we hope you enjoy this contest and have fun!

Of course, this contest will be unrated.

Updated: the editorial has been released! Please refer to the link in the contest's local website.

কি অবস্থা ব্রো? আবারও চলে এসেছি! (That's Bengali for "What's up bro? I am back again!")

I am super excited to invite you to participate in CodeTON Round 9 (Div. 1 + Div. 2, Rated, Prizes!) which will be held on Nov/23/2024 17:35 (Moscow time). This round is rated for both divisions.

The contest will feature $$$8$$$ problems, with three of them divided into two subtasks each. You will have $$$3$$$ hours to solve as many as you can. The problems are authored and prepared by me and wuhudsm.

I would like to thank -

• TheScrasse and Kaey for their jaw-dropping (literally) coordination of the round, giving valuable feedback and improving lots of problems.
• wuhudsm for being kind enough to use one of his cool problems in the round.
• Alpha_Q and Raiden for discussing tons of problems with me and improving some problems.
• antontrygubO_o for sacrificing his TON by not participating in the round as he knows some of the problems as my past coordinator.
• dorijanlendvaj, wyrqwq, Alpha_Q and nfssdq for being our MVP testers and improving the round immensely.
• Thienu, wuhudsm, jdurie, Farhan132, Soumya1, redpanda, LMeyling, upobir, AlephZero01, NemanjaSo2005, tb_ro, Kawchar85, waidenf, serotonin, dazlersan1, I_Love_you_Tithi, Random_3652, Raiden and LipArcanjo for testing and improving the round as well.
• redpanda for creating awesome Manim video editorials for some of the problems.
• The great MikeMirzayanov for the amazing Codeforces and Polygon platforms.
• You, for existing and participating in the round. Also, thanks for giving your best and not quitting. You will get what you want prettyyy soon. Just hold right there .

Score distribution:
$$$500 - 1000 - (1000 + 1500) - 2000 - 2750 - (2000 + 2000) - 4250 - (2250 + 2500)$$$

Wishing you TONs of luck — hope you have a TON of fun cracking the problems!

UPD: Editorial

UPD: Congratulations to the winners!

1. orzdevinwang
2. tourist
3. Rewinding
4. Kevin114514
5. maspy
6. Radewoosh
7. ksun48
8. jiangly
9. cn449
10. maroonrk

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 9.

The Open Network (TON) is a fully decentralized layer-1 blockchain designed to onboard billions of users to Web3.

Since July 2022, we have been supporting Codeforces as a title sponsor. This round is another way for us to contribute to the development of the community.

The winners of CodeTON Round 9 will receive valuable prizes.

The first 255 participants will receive prizes in USDT cryptocurrency in the TON network:

• 1st place: 2,560 USDT
• 2–3 places: 1,280 USDT each
• 4–7 places: 640 USDT each
• 8–15 places: 320 USDT each
• …
• 128–255 places: 20 USDT each

All participants will receive Soulbound Tokens (SBT) that reflect their developer rating

We wish you good luck at CodeTON Round 9 and hope you enjoy the contest!

Hi everyone!

For the Winter 2025 edition of the Osijek Competitive Programming Camp (OCPC), we are working with the National University of Singapore (NUS) to host a mirror of the OCPC in Singapore, during 22-26 Feb 2025. The mirror will consist of 4 training contests, that are a subset of the main 7 contest of the OCPC (scheduled for 15 Feb-23 Feb 2025 in Osijek, Croatia and online, will be officially announced later).

The contest days will be on 22, 23, 25 and 26 Feb, and 24 Feb will be a rest day. The mirror takes place right before ICPC APAC Championship 2025, scheduled for 27 Feb-2 Mar, and is a good training opportunity for its participants. Please note that the mirror is a private initiative of NUS and OCPC, and is not an official part of the ICPC event.

If you want to get a feel of the contests, refer to this comment for past public OCPC contests.

We are still looking for problem-setters for this edition's OCPC. If you are interested in problem-setting, please contact adamant. We are especially interested in problem-setters who can come onsite to give live editorials. Refer to this post for more details.

Registration

The participation fee for the mirror is 50 SGD per person, and it is only possible to participate in person. Please note that it does not include travel, accommodation or meal expenses. If you want to participate, please register here before 10 Feb 2025.

FAQ

Will the contest system be the same as the ICPC APAC Championships?
You will use the same physical set-up, but we will be in a different room in NUS. The online judge used will also very likely be different.

Are teams that are not attending the ICPC APAC Championships allowed to come?
Yes, you are welcome to come.

What is included in the costs?
In addition to the contest system and problems, snacks and a final dinner will be included in the costs. Again, it does not include travel, accommodation or meal expenses.

If you have any other questions, please write them in the comments below!

Note that initially this contest was scheduled on a different day. Due to technical difficulties, we had to postpone the online mirror. We are sorry about that; if you planned to participate, but are no longer able because the contest day has changed, you can use the virtual participation option.

Hello Codeforces!

The Southern and Volga Russian Regional Contest was held in Saratov State University yesterday, on 12th of November. This contest was used to qualify the teams from Southern Russia and Volga region to the Northern Eurasia Finals.

On Nov/18/2024 13:35 (Moscow time), 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.

The contest was prepared by adedalic, awoo, dmitryme, elena, Neon, DmitryKlenov, MikeMirzayanov, Ferume and me. Big thanks to the contest testers: Kuroni, ashmelev, bthero, KIRIJIJI, Kniaz, vladmart, JanPlovLagman, H3nTa1, pshenikita. I would like to express my gratitude to MikeMirzayanov for not only participating in the preparation process himself, but also making Polygon, which made our work much easier.

As the chief judge of the contest, I hope you enjoy the problems!

Of course, the contest will be unrated.

Welcome to Natlan, Codeforces!

Toyac Springs, Natlan

sum, vgoofficial and I are like a dog with two tails to welcome you to participate in Codeforces Round 988 (Div. 3) at Nov/17/2024 17:35 (Moscow time). We have cooked up $$$7$$$ problems to be solved in $$$2$$$ hours and $$$15$$$ minutes.

The round will be hosted by rules of educational rounds (extended ICPC). Thus, solutions will be judged on preliminary tests during the round, and after the round, it will be a 12-hour phase of open hacks. After open hacks all accepted solutions will be rejudged on successful hacks.

Note that the penalty for each wrong submission in this round is 10 minutes. Also, note the rule restricting AI use!!! If you are caught using AI in an unorthodox manner, bad things will happen to you. We will be watching you all...

IMPORTANT!!! There is at least one interactive problem in the problemset. Please familiarize yourself with the guide for interactive problems beforehand.

Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them)
• do not have a rating of 1900 or higher at any moment in time.

Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you (unless you register unrated).

We would like to orz the following individuals for making the contest possible:

• Vladosiya for the pogU coordination.

• Our army of testuwuers: (VIP) Dominater069, amoeba3, LMeyling, awesomeguy856, AlperenT, Error_Yuan, 18o3, Intellegent, efishel, Edeeva, Lilypad, wuhudsm, Vladosiya, Filikec, kevlu8, (VIP) chromate00, Prady, mathtsai, AdityaTakkar, larush, RobinFromTheHood, macaquedev, and dazlersan1.

• MikeMirzayanov for being MikeMirzayanov.

UPD: Editorial!!!