Dear Santa Claus. Please make 2023 a happy year, not just that. Please, we all need this.

Hello, 2023!

And we have traditional gifts!

Change Handle Feature

Hurry! Only until the 10th of January, you can change your handle (but only once)! Note that it will be possible to roll back the changes or change the handle again only after a year. Be careful what you wish for.

You can change your handle to the new one which wasn't used before by anybody or which was used by you before. The links to a profile page with an old handle would automatically redirect to the actual profile.

Again, this year if you took part in at least 10 rounds you can request a handle of an inactive participant. It means that the participant should have a period of activity on Codeforces of at most 180 days, this period should be in 2020 or earlier. The inactive participant can't have posted comments, messages, and so on. It can't take part in more than 2 contests. It will be automatically renamed and informed by email. A user has the opportunity to request back his/her handle: in this case, we will roll back the change and return your previous handle to you. If you can't change your handle to another, it means that some requirements don't meet. Please do not ask me to do something with it. Especially, I do not like requests like "this is my second account, I took an interesting handle myself". I'm not Santa Claus.

Talking about handles I always
reminisce the following story. Once a user wrote me the 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 the profile setting. Happy New Year!

Hello, Codeforces!

We are pleased to announce the second “Hello Muscat 2023” ICPC programming bootcamp, the continuation of the “Hello” bootcamp series, organised by Harbour.Space University, in collaboration with PhazeRo, Gutech, UK Oman Digital Club, Leagues of Code, Gutech CS Club and Codeforces!

We are inviting all of you to join us from March 8th to March 16th, 2023 in Muscat, Oman for an intense 8 days of programming! It is not only a great opportunity to train but also a chance to discover a new amazing country. There are many reasons why you must visit Oman at least once in your life, from its great people to its natural beauty and surrounding peace. March is an especially great time to visit Oman if you want to enjoy nice beach weather — don’t miss it!

As always, we can’t wait to see you there to learn, practice and compete on the international stage, smoothing your road towards the joined World Finals 2022 and 2023 in Egypt!

Our coaching line-up combines talent and experience, featuring ICPC world champions winners and finalists, as well as legendary names from the field of competitive programming: Mike Mirzayanov MikeMirzayanov, Kamil Debowski Errichto, Yahor Dubovik 244mhq, Artem Plotkin Rox, Maksym Oboznyi MaksymOboznyi and Nikolay Budin budalnik.

It will be an amazing opportunity for teams from all over the world to learn from these well-known and successful coaches in the ICPC world!

The Bootcamp will be split into three divisions:

• Division A. Division A will be a mirror of the Petrozavodsk Programming Camp. Suitable for teams who already qualified for the world finals ICPC or are aiming that high. Participants of division A will be solving contests in the same conditions as a real competition to perform with more confidence in the ICPC world finals.

• Division B. Designed to help teams prepare for the next season of ICPC regional competitions. Appropriate as an introduction for teams and students just getting their foot in the door of the world of ICPC and competitive programming competitions in general. Division B will have thematic contests and lectures.

• Division C. Designed for newcomers to the world of ICPC competitive programming. For those with a handle on the basics but want to compete in future competitions and possible regionals, this division is the perfect starting point.

Types of participation: On-Site and Online

We believe that participation in our Bootcamp should be accessible by all teams wherever they are and that is why we made onsite and online types of participation.

20% Early Bird Discount is offered to universities and participants who register and pay before Jan 31st 2023.

You can ask any questions by email: [email protected]

Hello Psyho, this is Mike. We are happy to help with likes. So, Codeforces?

He waits for your likes here: https://twitter.com/FakePsyho/status/1605570944537280512?t=MV0OksdeUb8FXKApncDZcw&s=19

I believe that 40 facts are too few for us. We need more!

Hello, Codeforces!

Cybros, the competitive programming club of LNMIIT Jaipur, is happy to invite you to participate in Codeforces Round 840 (Div. 2) and Enigma 2022 - Cybros LNMIIT which will be held on Dec/19/2022 17:35 (Moscow time).

You will be given 6 problems and 2 hours to solve them. The round will be rated for participants with rating strictly less than 2100. Division 1 participants can also participate unofficially in the round.

The problems were prepared by me, DreadArceus, ...nvm, warks, .utk., and og_. We would like to thank:

• Aleks5d for coordinating the round and translating the statements into Russian,
• svince, tankman890, SoCloseButStillSoFar, shiviDON, abhigyan10, and pulkit_jain for discussing problems and coming up with problem ideas that didn't make it to the final problem set,
• KAN, satyam343, GoatTamer, physics0523, MasterRayuga, blitztage, weakestOsuPlayer_244, Gaurav3478, 18o3, jainmilind, Milind_Sharma, DragoPhoenix, Nitin1605, AloneMusk, master._.mind, TarunAga, gaurav1910, mePrakhar, 4qqqq, LoLZeS666, PHOENIX_RISER, WORTH, athern27, sleepinGiant, and C-3PO for testing the problems and providing invaluable feedback, and
• MikeMirzayanov for the great platforms Codeforces and Polygon.

Good luck and have fun!

UPD1: Score distribution is 500 — 1000 — 1500 — 2000 — 2000 — 3000

UPD2: Congratulations to the winners!
Overall:
1. tourist
2. Um_nik
3. gyh20
4. neal
5. noimi

Div. 2:
1. apei
2. yyyz04
3. bobbilyking
4. rainboy
5. RNS_JK

UPD3: The editorial has been published.

About Enigma

Enigma is a part of Plinth 2023, LNMIIT Jaipur's tech fest. If you are an Indian school/college student, we will also hold an onsite round of Enigma from 27 to 29 January, 2023. You can register for the onsite round by filling the google form on our Instagram page.

As a part of Plinth, we will also conduct IUPC (Inter University Programming Contest), which is an ICPC-like contest for teams of three people. This contest is good practice for the real ICPC rounds. Both Enigma onsite and IUPC will have cash prizes and goodies.

Привет, Codeforces!

В 18.12.2022 17:35 (Московское время) состоится Codeforces Round 839 (Div. 3) — очередной раунд для третьего дивизиона. В этом раунде будет 7 задач, по сложности подходящих для участников с рейтингом до 1600 (во всяком случае, мы надеемся на это). Но, конечно же, участники с рейтингом 1600 и выше могут зарегистрироваться на раунд вне конкурса.

Раунд пройдет по правилам образовательных раундов. Таким образом, во время раунда задачи будут тестироваться на предварительных тестах, а после раунда будет 12-ти часовая фаза открытых взломов.

Вам будет предложено 7 задач на 2 часа и 15 минут. Мы надеемся, что вам они покажутся интересными.

Напоминаем, что в таблицу официальных результатов попадут только достоверные участники третьего дивизиона. Как написано по ссылке — это вынужденная мера для борьбы с неспортивным поведением. Для квалификации в качестве достоверного участника третьего дивизиона надо:

• принять участие не менее чем в двух рейтинговых раундах (и решить в каждом из них хотя бы одну задачу),
• не иметь в рейтинге точку 1900 или выше.

Независимо от того, являетесь вы достоверными участниками третьего дивизиона или нет, если ваш рейтинг менее 1600, то раунд для вас будет рейтинговым.

Раунд основан на задачах муниципального этапа Всероссийской олимпиады школьников в Саратове и Саратовской области, поэтому если вы участвуете в нем — пожалуйста, воздержитесь от официального участия в этом раунде.

Задачи вместе со мной придумывали и готовили Адилбек adedalic Далабаев, Иван BledDest Андросов и Максим Neon Мещеряков. Выражаем свои благодарности тестерам раунда: ermukanoff, soup, lankin.i, Fanarill, stAngel и senjougaharin. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Удачи в раунде! Успешных решений!

UPD: Разбор опубликован

Hello, Codeforces!

Winter holiday is coming! And we are excited to invite you to our third round, Polynomial Round 2022 (Div. 1 + Div. 2, Rated, Prizes!), which will be held on Dec/17/2022 17:35 (Moscow time). You are given 8 problems and 2.5 hours to solve them.

All problems were written and prepared by Ecrade_, Little09, ChthollyNotaSeniorious, JianfengZhu, Cirno_9baka, mejiamejia and me.

And thanks to dorijanlendvaj, gisp_zjz, gamegame, triple__a, Chenyu_Qiu, Suiseiseki, aaaaawa, leukocyte, waaitg, Kubic, LHQing, RedLycoris, lucaperju, njupt_lyy, Kilo_5723, Huah, prvocislo, foreverlasting, thanhchauns2, Rhodoks, JohnVictor, Psychotic_D, VinstaG173, dannyboy20031204, 4qqqq, CoupDeGrace, NetSpeed1, 5ab, Lavine, absi2011, UtopianZ for testing and good advice, antontrygubO_o for his excellent round coordination and help with preparation and MikeMirzayanov for great systems Codeforces and Polygon.And you, for participating!

This is our third round! Although you may find members in our team and testers who helped are not the same as the past, our permanent love and enthusiasm for coding will not change. Conspicuously, great efforts have been put in it. We are sincerely looking forward to your participation and we hope everyone will enjoy it. Besides, this round is sponsored, which indicates that everyone has an opportunity to get the prize!

UPD1: Here is the score distribution:

500 — 1000 — 1500 — 1500 — 2000 — (1500 + 1000) — 3250 — 4000

UPD2: Sorry to everyone! We must apologize because the pretest of B is not strong, leading to FST for many people. It is our fault! We don't want to make excuses. This time, we did a bad job and let everyone down. We all blamed ourselves sadly. Although we have invited a lot of testers but most of them passed all the tests, and even some of them get 'WA', they fixed their code and passed it. So we didn't pay too much attention to it -- we thought it was 'normal'. However, we didn't suppose the pretests were so weak that lots of participants get FST. Sorry again! (>_<)

And personally, firstly, I must apologize to all of you. I let you down this time. I blamed myself sadly. And I accept all the critical opinions. However, secondly, I know that you must feel angry when you find your B got FST, and that's all our fault, but because my birthday is coming, I intended to use this contest to record the growth of me and my team members, as well as my happy memories on codeforces, so could you please don't scold me too harshly when criticizing me? (Actually I am crying when typing this words; I blamed myself sadly when I saw lots of FST). I will regard all your comments as the most valuable things which urge me to become a better person and help me grow to a more mature person, but maybe I will be very painful if I see comments or messages as 'you are a trash''trash round'. (⑉꒦ິ^꒦ິ⑉)

Sorry! We did a bad job because of our carelessness this time, but we promise we will try our best to improve our comprehensive abilities, and bring a better round next time! We will keep in mind every word of encouragement and criticism, which is the driving force for our growth. Wish you happy everyday! (•ω•)

UPD3: Tutorial is available.

Thanks for all the warmth and kindness!!! I felt deeply guilty during the past few hours, now I feel better. I really appreciate your warmth and kindness!!! (●'◡'●)

We made the contest just because we would like to share our interesting ideas with you. If you like any of the ideas, we will be very delighted!!! o(≥ω≤)o

UPD4:Congratulations to the winners

1. Um_nik
2. maroonrk
3. tourist
4. inaFSTream
5. ksun48
6. LJC00118
7. ugly2333
8. bruhopen
9. ecnerwala
10. heuristica

And for my personal gifts: the two random number is 91 and 1028, so congratulations to sd0061 and regain0001!!! (The rank contained the virtual participants at that time, which improves randomness, only if the time and the rank both accorded with the number , you can get the gifts!!!) o(〃'▽'〃)o

Thanks to all the warmth and kindness!!! You really light up my heart!!! We will try our best next time and prepare a better round to share our interesting ideas with you!!! ✧⁺(๑•ω•๑)⁺✧

And here is the information from our title sponsor:

Prizes

The participants who end up in the first 255 positions will receive prizes. The participant on the first place will receive $256, the next two participants will receive $128, the next four participants will receive $64, etc. Prizes will be distributed in OP (Optimism) tokens.

About Polynomial

Polynomial is building in decentralized finance – a more fair, accessible, efficient, and transparent financial system enabled by crypto. Polynomial automates financial derivative strategies to create products that deliver passive yield on various assets. Polynomial Earn is the first DeFi Options Vault (DOV) that executes completely on-chain by selling options directly to an AMM.

If you have a background in mathematics or software engineering and a knack for problem-solving, we want to hear from you. You will have the opportunity to work on cutting-edge technology and tackle complex problems alongside a talented and driven team.

By joining us at this early stage, you will make fundamental decisions that will shape the course of Polynomial. We prefer passionate, quick learners with a history of excellence.

Find out more about us on our website polynomial.fi or texting rivalq.

If you wish to be part of our remote-first team or apply for an internship, please fill in the form or email [email protected]. Make sure to apply before Dec 20, 2022.

We wish everyone good luck and have a positive delta!

Привет, Codeforces!

В 16.12.2022 17:35 (Московское время) состоится Educational Codeforces Round 140 (Rated for Div. 2).

Продолжается серия образовательных раундов в рамках инициативы Harbour.Space University! Подробности о сотрудничестве Harbour.Space University и Codeforces можно прочитать в посте.

Этот раунд будет рейтинговым для участников с рейтингом менее 2100. Соревнование будет проводиться по немного расширенным правилам ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением, равен 10 минутам. После окончания раунда будет период времени длительностью в 12 часов, в течение которого вы можете попробовать взломать абсолютно любое решение (в том числе свое). Причем исходный код будет предоставлен не только для чтения, но и для копирования.

Вам будет предложено 6 или 7 задач на 2 часа. Мы надеемся, что вам они покажутся интересными.

Задачи вместе со мной придумывали и готовили Адилбек adedalic Далабаев, Владимир vovuh Петров, Иван BledDest Андросов, Максим Neon Мещеряков и Алексей shnirelman Шнирельман. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Удачи в раунде! Успешных решений!

Также от наших друзей и партнёров из Harbour.Space есть сообщение для вас:

Harbour.Space University в сотрудничестве с Noventiq, ведущим мировым поставщиком решений и услуг в области цифровой трансформации и кибербезопасности, предлагает возможность работать и учиться в Барселоне специалистам по данным. Мы стремимся распределить стипендии для интенсивных учебных программ на самом высоком уровне для подходящих кандидатов, которые смогут присоединиться к нашему путешествию.

Кандидаты будут работать над выполнением следующих задач:

• Изобретение и внедрение подходов к решению задач компьютерного зрения и машинного обучения, формирование требований совместно с командой;
• Планирование экспериментов, обучение моделей, оценка их качества и встраивание в пайплайны;
• Работа с данными, формирование ТЗ для разметки;
• Регистрирование результатов обучающих прогонов моделей и отслеживание динамики их выполнения;
• Написание алгоритмов пре- и постобработки изображений и видео, логики сценариев обработки медиаданных;
• Проведение исследований в области компьютерного зрения: классификация, обнаружение, сегментация;
• Оптимизация нейронных сетей: дистилляция, квантования, обрезка;
• Подготовка моделей для производства;
• Проведение разработки пользовательских алгоритмов и модулей нашей платформы видеоаналитики.

Все успешные кандидаты будут иметь право на получение стипендии со стопроцентной оплатой обучения (22 900 евро в год), предоставляемой Noventiq для Data Science.

ОБЯЗАТЕЛЬСТВА КАНДИДАТА

Обучение: 3 часа в день

За год обучения вы завершите 15 модулей (длительность каждого 3 недели). Ежедневная учебная нагрузка составляет 3 часа, плюс домашнее задание, которое нужно выполнить в свободное время.

Работа: 6 часов в день

Погрузитесь в профессиональный мир во время обучения. Вы будете учиться у лучших и с первого дня сможете применять свои новые знания на практике.

Требования университета

1. Степень бакалавра в области математики, статистики, науки о данных, информатики или аналогичных областях
2. Знание английского языка

Требования к работе

• Экспертные знания и опыт в Python, а также в TensorFlow/PyTorch;
• Опыт внедрения моделей углубленного обучения для коммерческих проектов;
• Опыт решения реальных задач в области компьютерного зрения;
• Опыт работы с Linux OS, Git, Docker;
• Понимание принципов работы современных популярных архитектур нейронных сетей;
• Владение культурой проведения экспериментов, вы знаете о воспроизводимости и протоколировании, можете объективно оценить качество модели;
• Владение испанским языком;

Удачи в раунде,

Harbour.Space University Team

UPD: Разбор опубликован

Hello, Codeforces!

amurto and I are glad to invite everyone to participate in Codeforces Round 838 (Div. 2), which will be held on Dec/15/2022 17:35 (Moscow time).

This Round will be rated for participants with rating strictly lower than 2100. Participants from the first division are also welcomed to take part in the competition but it will be unrated for them.

You will be given 7 problems and 2 hours and 30 minutes to solve them. One of the problems will be interactive. Make sure to read this blog and familiarize yourself with these types of problems before the round!

We would like to thank:

• errorgorn for amazing coordination and help with the problem preparation.
• KAN for translation of the statements into Russian
• TheScrasse for providing suggestions which helped us to improve one problem.
• GoatTamer for discussing problems with us while our proposal was in review and testing the round.
• dorijanlendvaj, Um_nik, tabr, jeroenodb, Kira_1234, rivalq, thenymphsofdelphi, MagentaCobra, prvocislo, towrist, maomao90, IceKnight1093, AGRU, Omja, ntherner, TheScrasse, Perpetually_Purple, priyanshu_bhardwaj, Nahian9696, koderkushy, Non-origination, brobat, jampm, nyaruhodo, the_hyp0cr1t3, iLLusio, Utkarsh.25dec, ak2006, AlperenT, physics0523, udhavvarma03, welleyth, meme, SlavicG, MasterRayuga, recurecurring, dedsec_29, blitztage, Mo2men and tibinyte2006 for testing this round and providing feedback.
• MikeMirzayanov for great Codeforces and Polygon platforms.

Score distribution is 500 — 1000 — 1750 — 2000 — 2500 — 2750 — 3500.

UPD1: Congratulations to the winners!

Overall:

• jiangly
• antontrygubO_o
• Hyperbolic
• tute7627
• A_G

Rated:

• _gxyd
• NoPotato
• Alphaqwq_
• MironRaisa
• Hanasaki

UPD2: Editorial is out.

We are looking forward to your participation!

Привет, Codeforces!

В 12.12.2022 17:35 (Московское время) состоится Educational Codeforces Round 139 (Rated for Div. 2).

Продолжается серия образовательных раундов в рамках инициативы Harbour.Space University! Подробности о сотрудничестве Harbour.Space University и Codeforces можно прочитать в посте.

Этот раунд будет рейтинговым для участников с рейтингом менее 2100. Соревнование будет проводиться по немного расширенным правилам ICPC. Штраф за каждую неверную посылку до посылки, являющейся полным решением, равен 10 минутам. После окончания раунда будет период времени длительностью в 12 часов, в течение которого вы можете попробовать взломать абсолютно любое решение (в том числе свое). Причем исходный код будет предоставлен не только для чтения, но и для копирования.

Вам будет предложено 6 или 7 задач на 2 часа. Мы надеемся, что вам они покажутся интересными.

Задачи вместе со мной придумывали и готовили Адилбек adedalic Далабаев, Владимир vovuh Петров, Иван BledDest Андросов и Максим Neon Мещеряков. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Удачи в раунде! Успешных решений!

UPD: Разбор опубликован

Hello, Codeforces!

I am glad to invite everyone to participate in Codeforces Round #837 (Div. 2) , which will be held on 11.12.2022 18:35 (Московское время)

Please note the unusual time!

The round will be rated for participants of Division 2 with a rating lower than 2100. Division 1 participants can participate unofficially in the round.

You will be given 6 problems and 2 hours to solve them. This round was prepared by me and 4qqqq.

I'd especially like to thank:

• Aleks5d for awesome coordination of our round.
• MikeMirzayanov, for the amazing Codeforces and Polygon platforms.
• ashmelev, TurboPiKachu, divanik, olya.masaeva, nnv-nick, neohacker, PavelKorchagin and Kolychestiy for testing the round and providing valuable feedback.

This is my first official round on Codeforces. We are sincerely looking forward to your participation. We hope everyone will enjoy it.

The score distribution : 500 — 1000 — 1750 — 2250 — 2750 — 3500

We wish you good luck and high rating!

UPD1: We know about problem with C task. Now we are trying to fix it.

Editorial.