Hello Codeforces,

After decades of hard work and several quality reviews from independent third parties, I'm delighted to invite you to participate in Codeforces Round 1073 (Div. 1), and, if you really want to, Codeforces Round 1073 (Div. 2), which will both held on 17.01.2026 17:35 (Московское время).

In each division, you will be given $$$7$$$ problems and $$$3$$$ hours to solve them, one of which will be divided into subtasks. Problems were mainly authored by me, nifeshe, with help from nika-skybytska and satyam343. Only $$$6$$$ or $$$7$$$ problems will not be interactive in each division, so please make sure to read the guide for interactive problems before the contest.

In related news, we’ve already been awarded the Nobel Peace Prize for this round, for achieving a level of problem quality so universally accepted that all global conflicts have been resolved.

I would like to thank the following people for making the contest possible:

• satyam343 for outstanding coordination and helping with problem ideas/preparation.
• Um_nik for preliminary reviewing the round.
• Sana for being the most helpful tester I've ever seen.
• EvenImage, Geothermal, A_G, sammyuri, _istil, Intellegent, catgirl, Dragos, weirdflexbutok, Hori, samsoom, whiitex for VIP testing.
• The rest of our testers: LipArcanjo, Adam_GS, __baozii__, jiazhichen844, maomao90, IceKnight1093, wangmarui, caterpillow, -firefly-, arvindr9, djm03178, omsincoconut, CatsAreCool, reirugan, conjectureguy, SpyrosAliv, chromate00, Non-origination, beaten_by_ai.
• Alexdat2000 for translating the problems to Russian.
• MikeMirzayanov and KAN for the Codeforces and Polygon platforms.
• And You for participating!

The score distribution will be announced later.

Unlike other rounds, this one will only be held once, so I sincerely hope you will not skip the round and enjoy all of the problems.

Hello, Codeforces!

The TG channel team @KogutIvanTutoring is pleased to invite you to participate in the first Div. 3 round of this year — Codeforces Round 1072 (Div. 3) on Jan/12/2026 17:35 (Moscow time). This round will feature 6-7 problems selected in difficulty to create an interesting competition for participants with ratings up to 1600. However, anyone with a rating of 1600 or higher can register for the round out of competition.

The round will follow the rules of educational rounds. Thus, during the round, the problems will be tested on preliminary tests, and after the round, there will be a 12-hour phase of open hacking. After this phase, all successful attempts will be retested on successful hacks. We have tried to create decent tests — just like you, we will be disappointed if many solutions fail after the contest ends.

You will be offered 6-7 problems and 2 hours 15 minutes to solve them.

The penalty for an incorrect attempt in this round will be 10 minutes.

We remind you that only reliable participants of the third division will be included in the official results table. As stated in the link — this is a necessary measure to combat unsportsmanlike behavior. To qualify as a reliable participant of the third division, you must:

• participate in at least five rated rounds (and solve at least one problem in each of them)
• not have a rating point of 1900 or higher.

Regardless of whether you are a reliable participant of the third division or not, if your rating is below 1600, the round will be rated for you.

The problems were conceived and prepared by part of our team: fstilus, Friendiks, gravitsapa, EzikBro, Boodoochai

Also, a big thank you to:

• MikeMirzayanov for the Polygon and Codeforces systems.

• Vladosiya for coordinating the round.

• misha.arkhipov, Escapisst, feblokas, lewc, mlovbnee, Yassia, YamOCHca, -_TIMOFEY_-, _liravel_, Gmacem, vintermach, margothequeen, itz_pabloo, sivukhin, Merkurev, the_dragon_emperor, Cyber, MariamH, Arpa, Marckess for testing of the round.

Good luck to everyone!

UPD. Editorial is out!

Happy new year, Codeforces!

We are glad to invite you to take part in Hello 2026, which will start on Jan/07/2026 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 wangmarui, Gold14526, Hoks_, Neil_Qian, Network_Error, jiazhichen844 and xvchongyv.

We would like to thank:

• Um_nik for pre-reviewing the round.
• Proof_by_QED for his wonderful coordination.
• Alexdat2000 for Russian translation.
• Geothermal, StarSilk, and Dominater069 for nutella testing.
• Mindeveloped, ETO_leader, nldr, max0810, A_G, _istil, ian_HLX, nifeshe, paulzrm, sammyuri, catgirl and Intellegent for red testing.
• cuteSubtask, LucaLucaM, cry, Genius_Star_rgw, Friedrich, incra, lkrqwq, LaDeX, pichax, shiny_shine, efishel, Edeeva, Register, AksLolCoding, Watersphere, Lilypad, tzl_Dedicatus545, Caylex and waauto for yellow testing.
• NATO, Cfz_qwq, MagentaCobra, gza, wuhudsm, madlogic and Heartquake for purple testing.
• tybbs, larush, pianapolataa, Terminator-XII, hollis_yang, Nukumizu-Anna, shengxuanyi, chromate00 and cby_ for blue testing.
• wizardMarshall, Solwek, sztcodeforces and lottle1212 for cyan testing.
• yaotianhao0906, lovelyfish and YSY_ for green testing.
• chenzhishuo2012 and doraimota for gray testing.
• Lynette_D for unrated testing.
• MikeMirzayanov and KAN for the great Codeforces and Polygon platforms.
• You for participating in this round.

Score Distribution: $$$500 - 1000 - 1500 - (1000 - 2000) - 2250 - 2750 - 4000 - 4000 - (4500 - 1000)$$$

Good Luck & Have Fun!

Update 1: The score distribution have been changed a bit. In particular, problem I will be split into two subtasks.

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

Update 3: editorial — https://codeforces.com/blog/entry/149944

Update 4: Congratulations to the winners!

1. maroonrk
2. ecnerwala
3. turmax
4. peti1234
5. kotatsugame
6. hos.lyric
7. BurnedChicken
8. strapple
9. stepanov.aa
10. antontrygubO_o

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