👋 Salam, Codeforces!

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

The Selection Round will be 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.
• 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 💸😉).

The score distribution will be shared closer to the contest date. 📊

We look forward to seeing you both online and onsite!

Good Luck & Have Fun! 🎉

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.

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!!!

Hello Codeforces!

We (pwned, ACGN, HappyPacMan, maomao90, AverageDiv1Enjoyer, and trunkty) are thrilled to invite you to Codeforces Round 987 (Div. 2) on Nov/15/2024 15:35 (Moscow time) (note the unusual time)! After more than two years of preparation and nearly thirty problems on our shortlist, our contest is finally here for your enjoyment!

In this round, you will help Penchick as he embarks on a world trip through the Philippines, Indonesia, and even through the Australian beaches and attempt six problems in two hours!

The score distribution will be as follows: $$$500-1000-1500-2000-2500-3000$$$.

This round would not be possible without the support of everyone behind this round:

• maomao90 and KAN for their excellent coordination and problem setting,
• pwned, ACGN, AverageDiv1Enjoyer, and trunkty for the creative tasks,
• HappyPacMan for his amazing technical skills in making the problems come to life,
• Alexdat2000 for translating problem statements,
• PiejanVDC, Shrimb, heavylightdecomp, ryuusama, and SlavicG for their unique problem ideas,
• ArvinCiu, Irmuun.Ch, bestial-42-centroids, dbscts, zscoder, NeroZein, and wfe2017 for their advice in creating interesting problems,
• _Body, ljuba, Dominater069, pavement, Rideris, Error_Yuan, NovusStellachan, Dan4Life, lunchbox, DilshodbekX, SHZhang, micho, Muhammad-Saram, culver0412, ErrorAssassin, AlperenT, iLoveIOI, newb_programmer, mwen, Erering, LMeyling, and AkiLotus for testing our round and providing invaluable feedback, and
• You for being an awesome member of the CF community!

Lastly, we thank MikeMirzayanov for creating the incredible Codeforces platform, where many of us have engaged in friendly competition, honed our problem-solving skills, and forged lasting friendships throughout the years!

From our keyboard to yours, we (and Penchick) wish you good luck, positive delta, and an exciting competition experience!

Note: There is at least one interactive problem, so please read the guide for interactive problems if you are unfamiliar with them.

UPD: Editorial has been posted, go check it out!

UPD: Congratulations to the winners!

Div. 1 + Div. 2:

1. tourist, as expected, fully solving all problems in 53 minutes
2. antontrygubO_o, who did so just 2 minutes later
3. noimi
4. A_G
5. Pyqe
6. StarSilk
7. dyppp
8. kotatsugame
9. busamate
10. tarjen

They, along with 8 other contestants, are the only AKers (full-solvers) in the whole contest!

Div. 2 only:

1. LGlcx, who full-solved in 100 minutes!
2. Sky_Maths
3. G2Esports
4. boboquack
5. ac_de_taffy
6. Jack.YT
7. Alex2184
8. MrPizza
9. priyanshu.p
10. CC_cccc

We hope you all enjoyed the round!

Hello Codeforces!

I am glad to invite you to Codeforces Round 986 (Div. 2), which will start on Nov/10/2024 18:35 (Moscow time). Note the slightly unusual start time.

The contest will run for 2 hours and have 6 tasks. The contest will only be rated for those with a rating not higher than 2099, but we welcome higher rated users to participate out of competition.

Holding the contest would have been impossible without:

• flamestorm for insanely excellent coordination, without whom this round would certainly not happen.
• Vince729 and swagchicken for lots of discussions about the problems and proposing other problem ideas :)
• conqueror_of_tourist, BucketPotato, Dominater069, sstrong, triple__a, xiaowuc1, lucasxia01, n0sk1ll, nikilrselvam, thanhchauns2, AkiLotus, bibimoni, CSQ31, mp1309, Non-origination, Qualified, redpanda, dazlersan1, fatant for testing and giving a ton of useful feedback!
• MikeMirzayanov for the wonderful Codeforces and Polygon platforms.

and of course a special thank you to all of you for participating!

Score Distribution: $$$500-1000-1500-1750-2000-2500$$$.'

UPD: The Editorial is now published.

UPD2: Congratulations to the winners!

Div 1:

1. jiangly
2. A_G
3. BurnedChicken
4. MAKMED1337
5. maspy

Div 2:

1. SUPERLWR-beta
2. mychecksdead
3. sweet_dream
4. contee
5. Sunflower233

First solves:

• A: podyapolskiy.yaroslav in 00:01:14
• B: potato167 in 00:07:38
• C: thembululquaUwU in 00:09:18
• D: jiangly in 00:17:37
• E: golions in 00:17:54
• F: MAKMED1337 in 00:10:29

Hello, Codeforces!

We (KDOI Team) are glad to invite you to take part in Refact.ai Match 1 (Codeforces Round 985), which is the 8th CP contest held by us! You can view the previous rounds by us here.

• Number of problems: $$$9$$$ ($$$0$$$ interactive);
• Start time: Nov/09/2024 17:35 (Moscow time);
• Contest duration: $$$180$$$ minutes;
• Score distribution: $$$750-1250-1750-2250-2500-3000-3500-5000-5500$$$.

The problems were authored and prepared by Error_Yuan, wyrqwq, Otomachi_Una and me sszcdjr.

A few words from our sponsor:

We’re Refact.ai, an open-source AI Coding Assistant, and on November 9th, we’ll be hosting our first round on Codeforces! Winners will receive valuable prizes, and all participants will have a chance to get some exclusive merch from us.

Refact.ai is pushing AI beyond simple code completion. Soon, we’ll launch the Autonomous AI Agent—a developer’s buddy that handles real engineering tasks end-to-end, from planning and coding to testing and deployment. You can read more about us in this announcement.

If you're excited about AI in software development and want to build the future instead of focusing on the trivial, join Refact.ai, founded by a former OpenAI researcher. We’re looking for talented Researchers and Backend developers to join our team.

Prizes:

• 1st place: 500 USDT
• 2nd place: 300 USDT
• 3rd place: 200 USDT
• 4-5th place: 100 USDT
• Top 50 participants will get T-Shirts
• Additionally, 50 random participants from the top 51-500 will receive a T-shirt

Good luck in the contest!

On the right, badges of the authors. From top to bottom, left to right are Error_Yuan, Otomachi_Una, sszcdjr and wyrqwq respectively.

We would like to thank:

• Vladithur for his wonderful coordination.
• Again, Vladithur for the Russian translation.
• programpiggy for providing a few unused problems.
• gyh20, dXqwq, Sugar_fan, 275307894a, Kubic, PEIMUDA, A_zjzj, LMydd0225, abc864197532, N_z__, rui_er, ProjectCF, chenyifanlx, MatrixGroup, wsc2008qwq, EasonLiang, cayaxi09, Hanghang007, SpadeA261, IwannaEATaCUTEcaca-qwq, OctoberEstuary, MrPython, acwing_gza, chromate00, mathtsai, Codula, tibinyte for testing and giving useful feedbacks.
• You, for participating and getting positive delta.
• Last but not least, MikeMirzayanov for great Polygon and Codeforces platforms.

Good Luck & Have Fun!

UPD1. The Editorial was published.

UPD2. Congratulations to the winners!

1. Benq
2. jiangly
3. hos.lyric
4. Radewoosh
5. arvindf232
6. Nachia
7. ksun48
8. Szoboszlai10
9. Endagorion
10. _Serge_