Hi Codeforces!

2025 comes to an end. However square the year was, we held a number of rounds: 29 Div. 1 and 31 Div. 2-only contests, to be precise! Additionally, 18 Div. 3, 4 Div. 4, and 13 Educational rounds made the schedule even more congested.

December is not only the perfect only time to wrap the year, but also to celebrate and thank all the people who made this year possible. That's why I want to highlight with this post the people whose efforts shaped Codeforces contests.

I'd like to say a huge thank you to every active community member who created and/or prepared problems for Codeforces rounds! Without your ideas and creativity, it would be impossible to hold so fun and interesting competitions. There are so many of you from every corner of the world, so that it's impossible to name everyone here, but one can see the authors of each contest on the contests page. Thank you!

Next, I'd like to extend my deepest gratitude to our coordinators who make sure rounds are the best quality and come on time. Here they are: Error_Yuan, maomao90, FairyWinx, Sugar_fan, satyam343, errorgorn, TheScrasse, 244mhq, Artyom123, Akulyat, Dominater069, flamestorm, abc864197532, cadmiumky, SSerxhs, Kaey, Vladithur, Um_nik, and Proof_by_QED coordinated Div. 1 and Div. 2 rounds this year. These people mostly worked after work of studies and sometimes even through the night to bring the rounds to you. An extra appreciation goes to Um_nik who now pre-reviews all round proposals, making sure the authors receive timely feedback. At the same time, BledDest and his team managed all the Educational rounds, Vladosiya managed all Div. 3 and Div. 4 rounds, with cry and soullless coordinating some of them. Thank you for your amazing work!

And last but not the least, I'd like to thank almost 800 testers who got to know the problems before the time, spotted some mistakes, and gave very useful advice to the problem authors. Again it's not possible to name them all, but huge shout-out to these heroes who tested the most rounds: _istil, chromate00, A_G, N_z__, larush, Error_Yuan, Proof_by_QED, Dominater069, __baozii__, Friedrich, -firefly-, madlogic, Um_nik!

Please join me in applauding all directly and indirectly mentioned people for their exceptional effort! Your work is invaluable for our community. Thank you! With that, I wish you all an exceptional New Year Eve and see you next year!

Hello Codeforces,

As 2025 comes to an end, it is time to start summing up the results.

This post is about the Global Rounds. Since September, we have held a series of three Global Rounds, numbered from 29 to 31.

This is the perfect moment to once again express our gratitude to XTX Markets for their initiative in organizing these rounds and their constant support over the years. Such stability in supporting the competitive programming movement is truly admirable and highly appreciated by the community. I wish XTX Markets a fantastic 2026, full of success and victories!

In each of the three rounds, 50 t-shirts were awarded (to the top 30 participants and 20 random participants ranked between 31st and 500th). This year, we had to change the manufacturing and shipping process, so it is still a work in progress, but things are moving forward, and shipping will begin soon. I would like to take this opportunity to ask the prize winners to respond promptly to any information requests and to meet the deadlines. It is also a good idea to keep your shipping address up to date at https://codeforces.com/settings/delivery.

The results for this series were calculated based on the best two performances out of the three possible rounds. Participants received points depending on their rank (points were awarded to the top 100 participants according to this table). The top 20 participants will receive commemorative hoodies and certificates indicating their rank.

Congratulations to the series winner ecnerwala on a decisive victory! Full results can be found at https://codeforces.com/contests/2147,2164,2180/gp100/best2/standings.

Thank you for participating in the rounds. Would you like another season of Global Rounds in 2026?

Mike

P.S. Here are the top 20 participants. Congratulations on winning a hoodie and a certificate!

Goodbye, 2025. Hello, 2026!

Dear Santa, Please make 2026 a happy year—not just for me, but for everyone. We all need this.

Hello, 2026!

And of course, we have our traditional gifts!

Change Handle Feature

Hurry! Until January 10, you can change your handle (but only once)! Note that next time you will be able to roll back the change or request another handle change only after a year (in December 2026). Choose wisely!

You can change your handle to a new one that hasn't been used by anyone else, or to one that you've previously used. Links to your old profile will automatically redirect to your updated profile.

Again this year, if you've participated in at least 10 rounds, you can request the handle of an inactive participant. This means the participant must have had a period of activity on Codeforces lasting at most 180 days, and this activity must have occurred in 2022 or earlier. The inactive participant must not have posted comments, messages, or similar content, and they must not have participated receiving 'Accepted' in more than 2 contests. In such cases, the handle will be automatically renamed, and the original owner will be notified via email. If the original user requests their handle back, we will roll back the change and restore your previous handle.

If you're unable to change your handle, it means some of the requirements have not been met. Please do not ask me to intervene manually. I especially dislike requests such as, "This is my second account; I took an interesting handle myself." I'm not Santa Claus!

Speaking of handles, I always reminisce about one particular story. Once, a user sent me this message: "Please change my handle from I_love_Valya to I_love_Sveta, as I no longer love Valya..."

New Year's Masquerade of Colors and Ranks

The traditional magical tab has appeared in your profile settings. Happy New Year!

Hello Codeforces!

The series of Educational Rounds continues thanks to the support of the Computer Science and Artificial Intelligence (CSAI) program at Neapolis University Pafos, with scholarships provided by JetBrains.

Educational Codeforces Round 186 (Rated for Div. 2) will start on Dec/29/2025 17:35 (Moscow time).

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 6-7 problems and 2 hours to solve them.

The problems were invented and prepared by Adilbek adedalic Dalabaev, Ivan BledDest Androsov, Maksim Neon Mescheryakov, Roman Roms Glazov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Big thanks to the testers FelixArg and KIRIJIJI for their valuable advice and suggestions!

Good luck to all the participants!

And on the occasion of the New Year — Happy New Year!

We wish you clear ideas, strong solutions, and many ACs in the year ahead.

UPD: Editorial is out

Merry Christmas, Codeforces! 🎄 🎄 🎄

We are glad to invite you to take part in Good Bye 2025, which will start on Dec/27/2025 17:35 (Moscow time). You will be given 9 problems and 3 hours to solve them. At least one problem will be interactive, so please make sure to read the guide for interactive problems before the contest. This round is open and rated for everyone.

Problems are authored by conqueror_of_tourist, twosquares, and YuukiS.

We would like to thank:

• Error_Yuan for his wonderful coordination.
• Alexdat2000 for Russian translation.
• Geothermal, Um_nik, and Dominater069 for nutella testing.
• __baozii__ for remaining an IGM during testing (unlike me).
• BucketPotato, kevinyang, golomb, xiaowuc1, apgpsoop, and 4fecta for red testing.
• kevin, Auchenai01, and _odium for testing and being an IM at some point in their lives (unlike conqueror_of_tourist).
• sszcdjr, fishy15, fwfjs, applepi216, beaaaan, zhed, Julto, and ow3nL for yellow testing.
• ToxicPie9, shcal, Gilwall, biximo, RTE, and aggrovector for purple testing.
• djrfrn, Leaves333, mtand872, chromate00, and mathtsai for blue testing.
• laze, LetianPie, RockingMat, and pranp_24 for cyan testing.
• waterbottledude for making sure we get every color (maybe you can test after the contest!!).
• Milmon and elituni for gray testing.
• jaguar713 for truly making sure we get every color (and drawing multiple diagrams).
• MikeMirzayanov and KAN for the great Codeforces and Polygon platforms.

• You

  for participating in this round.

Update 1: The score distribution is as follows

⛄ We hope you'll enjoy the problems! ⛄

Update 2: Hacks will be disabled on problems A-E.

Update 3: Editorial

Update 4: Congratulations to the winners!

1. jiangly
2. Benq
3. Kevin114514
4. VivaciousAubergine
5. ecnerwala
6. StarSilk
7. Radewoosh
8. Ormlis
9. ksun48
10. liuhengxi

We sincerely hope you enjoyed a nonnegative number of problems on the round. We hope you have a Happy New Year (both on CF and irl... maybe go touch some grass for the first time this year)!

Hello, Codeforces!

We are happy to invite you to an exciting online event: ICPC 2025 Online Winter Challenge powered by Huawei, which will start on December 26, 2025 11:00 UTC (UTC+0). In this Challenge, you will have a unique chance:

• to compete during 16 days online challenge
• to solve 1 exciting problem prepared by Huawei
• to win amazing prizes from Huawei!

As a special prize, Huawei together with ICPC Foundation will provide the travel and an invitation to the 50th Annual ICPC World Finals in a guest role!

Everyone is welcome to participate. It is an individual competition.

Start: December 26, 2025 11:00 UTC (UTC+0)

Finish: January 11, 2026 10:59 UTC (UTC+0)

Prizes

Challenge Rules and Conditions

By participating in this Challenge, you agree to the Conditions of Participation and Challenge Rules. If you cannot access this document, please email [email protected]

Good luck, we hope this will be fun!

We hope you'll enjoy this complex yet very exciting Challenge!

Hello, Codeforces!

IceBorworntat, NortGlG, omsincoconut, and I are excited to invite everyone to Codeforces Round 1071 (Div. 3), which will take place on Dec/23/2025 17:45 (Moscow time). You will be offered 8 problems, and you will be given 2 hours and 30 minutes to solve them.

Please note that this contest contains at least one interactive problem and at least one run-twice problem. Please read the guides for interactive problems and run-twice problems before the contest if you are unfamiliar with them.

The round will be hosted by the rules of educational rounds (extended ICPC). Thus, all solutions will be judged on preliminary tests during the round, and after the round, there will be a 12-hour phase of open hacks. After the open hack phase, all accepted solutions will be rejudged on successful hacks. Also, note that there is no score distribution—rank will be determined by number of problems solved, followed by penalty; wrong submissions will incur the usual penalty of 10 minutes, following the rules of educational rounds.

As a reminder, only trusted participants of the third division will be included in the official standings table. This is a compulsory measure for combating unsporting behavior. To qualify as a trusted participant of the third division, you must:

• take part in (and solve at least one problem in) at least five rated rounds
• and not have had 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).

For Codeforces contests—including this one—improper use of artificial intelligence is severely condemned.

We would like to thank:

• sleepntsheep, Marszpace for their problem contributions and valuable help during the preparation of this contest.
• cry for great coordination and support throughout the preparation process.
• MikeMirzayanov for great Codeforces and Polygon platforms.
• temporary1, LMeyling, Intellegent, Argentum47, SpyrosAliv, catgirl, ritam1234, Proof_by_QED, ttamx, tin.le2, Ermiooo158, Mysticmage45, efishel, kwant, gentlecoder29, macaquedev, chromate00, dazlersan1, ALnQ417 for testing the round.
• You for participating in the round.
• blackslex for no particular reason! Really, no reason!

We hope that you guys will enjoy the problems.

Editorial

Salam, Codeforces!

After many years, we are excited and pleased to announce that Codeforces Global Round 31 (Div. 1 + Div. 2) will be held on Dec/19/2025 17:35 (Moscow time). Thanks to XTX Markets for supporting the initiative! In 2025, we held 3 such rounds, and the series results will take into account the best 2 participations out of 3.

Codeforces Global Round 31 marks the third round in the 2025 series of Codeforces Global Rounds. These rounds are open and rated for everyone.

The prizes for this round are as follows:

• The top 30 participants will receive a t-shirt.
• 20 t-shirts will be randomly distributed among participants ranked between 31 and 500, inclusive.

The prizes for the 3-round series in 2025:

• In each round, the top-100 participants get points according to the table.
• A participant's final score will be the sum of the points they earned in their 2 highest-placing rounds.
• The top 20 participants across the series will receive sweatshirts and placement certificates.

We extend our gratitude to XTX Markets for supporting the global rounds initiative in 2025!

The problems for this round were prepared by MohammadParsaElahimanesh, Shayan, and me.

We would like to express our sincere thanks to:

• Akulyat for coordinating the round and providing valuable feedback throughout the process;
• the testers: N_z__, A_G, YuukiS, amirhoseinfar1385, ArshiaDadras, Millad, EyadBT, aimoon, michao, JeffreyLC, s.seraj.shafie, AminAnv1, abramazani, MRasool, Radman_, Hooded_Hood, tilnoene, PMiguelez, chromate00, M.H.N, CLown1331, and dina_saba for their time and effort in testing the problems;
• MikeMirzayanov and KAN for creating and maintaining the great platforms Codeforces and Polygon.

The round will feature 8 + 2 problems, and you will have 2.5 hours to solve them.

Score Distribution: $$$500 - 750 - 1500 - 1750 - 2000 - (2500 - 750) - 2750 - (3000 + 3000)$$$

Good Luck & Have Fun!

Editorial is out.

Congratulations to the winners!

1. ecnerwala

2. Kevin114514

3. kotatsugame

4. maroonrk

5. hos.lyric

6. tourist

7. JDScript0117

8. VivaciousAubergine

9. crazy_sea

10. qiuzx

Hi, Codeforces!

December is the perfect time to wrap up the year, and we’re happy to invite you to follow the final stages of the most important school and student team competitions in competitive programming. Mark your calendars: from December 15 to 17, the 26th Russian Team Olympiad in High School Programming Contest and the ICPC Northern Eurasia Finals 2025 will take place.

The official opening of the championships will be on Monday, December 15. The detailed schedule is available on the website.

On our accounts, we’ll be sharing updates about the participants and their results. As usual, we’ve put together a list of useful materials in a single post; it will be updated gradually so you can conveniently follow the progress of the competitions and cheer for your favorites. By the way, who do you think will become the champions of RTO HSPC and NEF?

ICPC Northern Eurasia Finals

The ICPC semifinals in our region celebrate their 30th anniversary this year — three decades of algorithmic contests that have brought together thousands of participants, hundreds of practice contests, months of preparation, multi-stage regional selections, and bright, inspiring victories. What anniversary surprises have the organizers prepared this year? Stay tuned for the news — it’s going to be exciting!

This season, nearly 3,000 teams took part in all qualification stages, and only 341 of them made it to the Northern Eurasia Finals. You can see how the regional contests went on the ICPC NERC page for this season on icpc.global, as well as in our gallery, where we’ve collected photos from the quarterfinals and qualification rounds. We also gathered team reactions from Saint Petersburg and Moscow during the quarterfinals — you can find them here.

The student team championship, as in previous years, is held in a distributed format across Saint Petersburg, Almaty, Novosibirsk, and Tbilisi. Already on Wednesday, December 17, the teams will face a crucial intellectual battle that will determine the finalists of ICPC 2026, who will represent Northern Eurasia on the world stage. The venue of the next final has not yet been announced, but we’re eagerly awaiting the news and guessing where it might take place.

For those who are not participating in the NEF, there will be an opportunity to solve the same problems in the “mirror” contest here on the platform. Registration is already open!

Join the live stream of the ICPC Northern Eurasia Finals contest on Wednesday, December 17, at 10:00 (utc+3), and the live stream of the closing ceremony scheduled for 17:00, to be the first to find out everything!

RTO HSPC 2025

On Tuesday, December 16, the main round of the RTO HSPC 2025 school team championship will take place. Based on the qualification results, 266 teams have been invited to compete. As with the student contests, the final round is held in a distributed format across several cities: 156 teams will compete at Lakhta Hall in Saint Petersburg, 72 teams in Almaty (Kazakhstan), 28 teams in Novosibirsk, and another 10 teams in Sirius.

The main round of the Russian Team Olympiad in High School Programming Contest, along with the live stream, will start on Tuesday at 10:00 Moscow time — join us to watch the next generation of young talents. We will find out who becomes the RTO HSPC champion later the same day during the closing ceremony live stream at 17:00.

Tag your favorites in the comments and wish them good luck!

Hello, codeforces ₍^. .^₎⟆

ABalobanov, Slamur and I are happy to invite you to participate in Codeforces Round 1070 (Div. 2), which will take place on Dec/11/2025 17:35 (Moscow time). This round will be rated for all participants with rating below 2100. You will be given 2 hours to solve 6 problems.

We are extremely grateful to these wonderful people

• The cutest coordinator FairyWinx.
• KAN, MikeMirzayanov for Codeforces and Polygon systems.
• Our amazing testers:
• Red-black testing: Um_nik.
• Red testing: A_G, Wansur, OG_Matveychick1, __baozii__, JoJo.
• Orange testing: aimoon, fractal, AlexanderGarifullin, Nyatl, antonis.white.
• Violet testing: dmkozyrev, yanb0, KiruxaLight, wuhudsm, Mosyagin.
• Blue testing: InsomniaT, atayawa, void_slowdown, kenzhik, rockoff, suharius, R1nixi.
• Green testing: emirhanbanan, ad1let17.

Score distribution:

We sincerely hope that you will enjoy the problems!

UPD: The editorial is out