Hello, my favorite community!

I’m in a hurry to tell you about a new event from our main sponsor — TON Smart Challenge #4!

An exciting 10 days contest that's open to both beginners and experienced FunC developers with a total prize fund of 30,000 TON begins on August 8th and lasts until August 18th, 23:59:59 UTC+4.

TON Smart Challenge #4 is designed to showcase the fundamental aspects of how smart contracts function in TON. Participants will have the opportunity to master complex cell manipulations, smart contract storage organization, comment handling, basic cryptography, and the logic of governance smart contracts through problem-solving.

To enter the challenge, simply register via the @toncontests_bot on Telegram. The bot will guide you through the registration process and keep you informed when the challenge starts, and the tasks are published. It will also help you submit your solutions as a legitimate participant.

More details about the contest and prize distribution one may find on the website.

But that’s not all the news!

In the early days of August was unveiled a new and improved TON Society.

TON Society, community of like-minded people united by the idea to contribute to the development of the TON ecosystem, has adjusted its philosophy and presents its improved version.

The mission of the upgraded community is to develop TON regional communities around the world, help enthusiasts organize offline meetings and attract local investors to work on TON projects.

To make this happen were established hubs in different regions worldwide:

• Europe
• SEA
• South Korea
• India

Builders and developers are welcome to join the TON Society and regional hubs.

Participating in TON Society means you’re aligning with the mavericks, forward-thinkers, the game-changers, and those who are shaping the world of TON.

Hello Codeforces!

We are pleased to invite you all to participate in Codeforces Round 891 (Div. 3), which will start on Aug/07/2023 17:35 (Moscow time).

The format of the event will be like any Div. 3 rounds:

• 6-8 tasks;

• ICPC rules with a penalty of 10 minutes for an incorrect submission;

• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)

• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated

• by default, only "trusted" participants are shown in the results table.

We encourage participants with a rating of 1600+ not to create new accounts but to participate unofficially.

Only trusted participants of the third division will be included in the official standings table. This is a forced 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 point of 1900 or higher in the rating.

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

Problems have been created and written by our team: FBI, Skillful_Wanderer, SashaT9 and Pa_sha.

We would like to thank

• MikeMirzayanov for creating Codeforces and Polygon.

• Vladosiya for coordination.

• nigus, YocyCraft, lis05, Nazar, welleyth, pavlekn, senjougaharin, Vladithur, DJeniUp, volochai, eggag32, moonpie24, shell_wataru, Kalashnikov, Bogdan1110, ksu_, zamong_juice, myav, sonyalytv for testing the round and making it better.

Good luck!

UPD: There was an error on problem F. We fixed the tests and rejudged solutions . We apologize for that. It only affected a few people whose solutions passes all tests now. Also some hacks were already added to the tests and broke some of solutions.

UPD2: Editorial

Hi, Codeforces!

Alexdat2000, Igorfardoc, and I are pleased to invite you to our Codeforces Round 890 (Div. 2) supported by Constructor Institute, which will be held on Aug/05/2023 17:35 (Moscow time). This round will be rated for participants with a rating lower than 2100.

We would like to thank:

• errorgorn for coordinating the round.
• Umi, maomao90, thenymphsofdelphi, Dominater069, Mike4235, valeriu, irkstepanov, zengminghao, Gheal, DeMen100ns, FEDIKUS, thanhchauns2, MinaRagy06, Java, xudian, madlogic, squishybanana04, stefanbalaz2, kobebryan9, Murinh0, IlyinAD, zamong_juice, Pemguimn, the_hyp0cr1t3, STommydx, peshkoff, AndZhi, revelcoS, Valenz, and tibinyte for testing the round and providing useful feedback.
• MikeMirzayanov for Codeforces and Polygon.

You will be given 5 problems, one of which is divided into two subtasks, and you will have 2 hours to solve them.

One of the problems will be interactive, so please read the guide for interactive problems if you are not familiar with it.

The score distribution is 500 — 750 — 1250 — 2000 — (1500 — 1500)

UPD: Tutorial

UPD2: Congratulations to the winners!

Div. 2:

1. AMDAM
2. Aoi_Minoa
3. baojiaopicua
4. Valaki2
5. JCY_

Div. 1:

1. neal
2. maspy
3. A_G
4. AmazingTalker_Frank
5. heno239

We are thrilled to share some exciting news with you! We are teaming up with our partner, Constructor Institute in Schaffhausen, Switzerland, to bring you an amazing opportunity: a round supported and organized in collaboration with Constructor Institute, where you can explore Master's programs in Switzerland. Now we pass the floor to our partner.

Hello, Codeforces community!

Constructor Institute in Schaffhausen (Switzerland) is pleased and proud to have the opportunity to support the round on Codeforces. We invite you to participate in it!

If you are passionate about studying in Switzerland and pursuing a Master’s degree, we encourage you to fill out the form to initiate the application process and scholarship interview. Our Institute representatives will be in touch with you to guide you through the next steps.

We offer two Master programs, both taught in English, with flexible duration of 1.5 or 2 years full-time:

• MSc in Computer Science, Software Engineering, and Leadership
• MSc in Quantum Software Engineering, and Computer Science

Our Master's programs open doors to a world of opportunities. Many of our students have secured high-profile roles in multinational companies in Switzerland and across the globe. Additionally, our programs also serve as an excellent preparation for Ph.D. research in fields such as software engineering, cybersecurity, artificial intelligence, and other advanced topics.

​​We understand that financing your education can be a concern, and to support your journey, we are offering the following scholarships:

• Tuition waiver scholarships — 20,000 CHF per year, covering the cost of tuition fees.
• Full scholarships — 20,000 CHF per year, covering the cost of tuition fees, along with a monthly stipend of 2,000 CHF to assist with living expenses in Schaffhausen.

Both scholarships are non-repayable, providing you with financial peace of mind.

To learn more about Constructor Institute and its programs, visit our webpage.

Eligibility for the programs and its available scholarships:

• You have obtained or you will obtain a Bachelor’s degree in Computer Science, Software Engineering, Physics, or a related field before the program starts.

To express your interest in this opportunity, please complete the form:

We wish you good luck in the competition and enjoy solving the problems.

Hello, Codeforces.

It's scary to think about it: there are already almost 1800 rounds in the list of past contests!

I started adding a filter to the table with these rounds. Right now, you can already filter by some of the types of rounds. Here's what I've supported:

• Div. 1
• Div. 2
• Div. 3
• Div. 4
• Div. 1 + Div. 2
• Educational Rounds
• CodeTON Rounds
• Globals
• Kotlin Rounds
• VK Cup Rounds
• Long Rounds
• April Fools

Of course, I might have forgotten some types of contests. Please remind me if I missed anything. We should pay attention only to types where we have conducted several contests of that type.

I plan to expand this filter by adding more settings. Perhaps it would be good to filter by the condition "has at least one submission in this contest" (or those for which no submissions at all). What do you think?

What else would you suggest adding?

P.S. Here is how it looks on the website (some intermediate version, some options may be missing).

I don't think comments like "you use X in model solution, author, are you an idiot?", "f**k you and your problems, they are shit" and such should be normal on Codeforces, especially when written by someone high-rated and/or respected in the community. I also don't think this kind of behavior should be normal towards regular users.

I know that sometimes contests can be frustrating. Sometimes it is the participant's fault, sometimes it is the problemsetter's fault, sometimes it just happens without anyone being guilty of that. And I understand that in some cases, the criticism the author receives is fair and well-deserved.

But there is a fine line between criticism, saying that you didn't like the problems, and hurling insults against the author. The former two are acceptable (and sometimes even needed, because authors have to improve and learn from their mistakes); the latter one, in my opinion, should not be acceptable.

It's not like we can ever get rid of offense and hatred completely; there will always be people who want to take it out on the community as a whole or someone specific. And if I created a blog for every time I saw an insult hurled towards me or some other member of the community, my account would already be banned for spamming. But I think that the comments like the one linked in the first paragraph are especially dangerous and need to be dealt with.

Codeforces community is biased towards people with high rating and people who do something for the website. And this is sometimes a good thing; but it can also make people think that if a high-rated participant and a problemsetter allows himself (or herself) to be rude and offensive, then it is acceptable, and they are allowed to do it as well. That's why cases like this one are especially bad.

We can never get rid of offense and hatred, but please don't make it something normal. Everyone should be responsible for what they are saying or writing, but if your word has some weight in the community, then it also means some additional responsibility for you. Please don't make people think that insulting the author (or anyone else, for that matter!) is perfectly reasonable and fine — I doubt you will like the results of that.

UPD: It looks like the focus of the comment section has shifted towards discussing how to give constructive feedback to the problemsetters. This is certainly one of the points of the blog, but the main thing I wanted to state was that insults against anyone should not be acceptable. It's just that the problemsetters usually get the most of the hatred on CF, so it's much easier to find the examples of that. But this behavior towards regular users should not be allowed either.

UPD2: Initially, there was a link to the comment which caused me to write this whole blog (a comment by a high-rated user and a problemsetter when he openly called another problemsetter retarded because of some details of the solution). I wanted to show it as a clear example, but it was not the right thing to do.

To the person whose comment I used as an example (if you're reading this): I apologize, I shouldn't have made it seem like you're the culprit, and I didn't understand the consequences of my blog fully. I know that you have openly admitted your mistake, and I admire you for that. If the fact that I've used you as an example made you feel awful, or made some other people call you out — I am terribly sorry.

Ciao, Codeforces! We're glad to invite you to take part in Codeforces Round 889 (Div. 1) and Codeforces Round 889 (Div. 2), which will start on Jul/29/2023 17:35 (Moscow time). You will be given 6 problems and 2 hours and 30 minutes to solve them in both divisions.

• One of the problems will be divided into two subtasks.
• One of the problems will be interactive, so please read the guide for interactive problems if you are not familiar with it.

The problems were authored and prepared by akifpatel, dario2994, Kaey and me.

We would like to thank

• dario2994 for his energetic coordination;
• Alexdat2000 for Russian translation;
• Vladithur, errorgorn for VIP testing;
• ALeonidou, antontrygubO_o, buffering, cry, emorgan, jamesbamber, MatteoArcari, MrBrionix, MyK_00L, pwned, zamong_juice for testing;
• MikeMirzayanov for creating Codeforces and Polygon.

Score distribution:

• Div. 1: $$$(750 + 750) - 1500 - 1500 - 2000 - 2750 - 3250$$$
• Div. 2: $$$500 - 1000 - (1250 + 1250) - 2500 - 2500 - 3000$$$

We hope you'll like the problemset!

Update 1: the editorial is out.

Update 2: congratulations to the winners!

Привет, Codeforces!

В Jul/27/2023 17:35 (Moscow time) состоится Educational Codeforces Round 152 (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, Михаил awoo Пикляев и Максим Neon Мещеряков. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Удачи в раунде! Успешных решений!

UPD: Разбор раунда опубликован.

Привет! В 25.07.2023 17:35 (Московское время) начнётся Codeforces Round 888 (Div. 3) — очередной Codeforces раунд для третьего дивизиона. В этом раунде будет 6-8 задач, которые подобраны по сложности так, чтобы составить интересное соревнование для участников с рейтингами до 1600. Однако все желающие, чей рейтинг 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. Мы постарались сделать приличные тесты — так же как и вы, мы будем расстроены, если у многих будут падать решения после окончания контеста.

Вам будет предложено 7 задач и 2 часа 15 минут на их решение.

Штраф за неверную попытку в этом раунде будет равняться 10 минутам.

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 пяти 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.

Задачи были придуманы и написаны нашей командой: myav, Aris, Gornak40, senjougaharin и Vladosiya.

Также большое спасибо:

1. MikeMirzayanov за системы Polygon и Codeforces.

2. tute7627 за красное тестирование раунда

3. oversolver, sevlll777, pavlekn, zwezdinv, Sokol080808, 74TrAkToR, vladmart, EJIC_B_KEDAX, Vladithur, KseniaShk, Be_dos за жёлтое тестирование раунда
4. moonpie24, FBI, meowcneil, NintsiChkhaidze, Phantom_Performer, SashaT9, spike1236, Kalashnikov за фиолетовое тестирование раунда
5. TheGoodest, Pa_sha, Sasha0738 за синее тестирование раунда
6. Syuzi777, Tahseen за бирюзовое тестирование раунда

Всем удачи!

UPD: Разбор

Hello Codeforcers!

I am pleased to invite y'all to participate in Codeforces Round 887 (Div. 1) and Codeforces Round 887 (Div. 2), which will start on Jul/23/2023 17:35 (Moscow time). In both divisions, you will be given $$$6$$$ problems and $$$2.5$$$ hours to solve them. The Div. $$$2 $$$ round will be rated for participants with rating below $$$1900$$$, while the Div. $$$1$$$ round will be rated for participants with ratings which are at least $$$1900$$$.

This round was authored and prepared by Benq, emorgan, omeganot, US3RN4M3, me (cry), Ina, nsqrtlog, buffering, ntarsis30, and ArielShehter.

We want to thank the following people for their contributions:

• Our amazing coordinator, darkkcyan, for the outstanding coordination despite the 12 hour time zone difference.

• The rest of our problemsetting team for being so eager to contribute their own problems and solutions, as well as testing the round: null_awe, oursaco, Apple_Method, wavelets, izhang, Whimpers, mirachael, Cereal2, asdf1234coding, and dutin.

• The rest of our testers for providing the feedback we needed to ensure our round was as enjoyable as possible: gamegame, rqi, penguinhacker, Umi, jonathanirvings, maxwellzen, GusterGoose27, NemanjaSo2005, willy108, EmeraldBlock, _Fake4Fun, eyangch, sum, amoeba3, Mike4235, awesomeguy856, thehunterjames, xiaossr, tgp07, QuangBuiCPP, Olympia, skye_, sayeem2004, ETL, Ask-2005, MorganWyoming, TonightV, jcai972, and ArcticCrusade.
• Alexdat2000 for translating the statements to Russian.
• MikeMirzayanov for the Codeforces and Polygon platforms.
• You for participating!

UPD 1: Score Distribution

Div. $$$2$$$: $$$500 - 1000 - 1500 - 2000 - 2500 - 3500$$$

Div. $$$1$$$: $$$500 - 750 - 1250 - 2000 - 2250 - 3000$$$

UPD 2: Editorial has been posted here

UPD 3: Congratulations to the winners!

Div.1

1. jiangly

2. Rebelz

3. Radewoosh

4. tourist

5. jqdai0815

Div. 2

1. dmaksym1177

2. Tmath_OneLove

3. onufryw

4. i_nevergive_up

5. clonegrandmaster

Good luck! Red panda wishes you all rating inflation!

Art credit to xiaossr

Hi everyone!

Sponsored by

After a successful camp last February (announcement, wrap-up), we are happy to announce that Osijek camp will be returning on 16.-24. September 2023 — just in time to prepare for the World Finals in November as well as several regional contests throughout the fall. The camp is hosted by the Department of Mathematics at J. J. Strossmayer University of Osijek and is brought to you by the organizing team of adamant, -is-this-fft- and ajovanov.

The camp is inspired by various competitive programming camps that we attended during our active years in ICPC, and is aimed to help college students prepare for ICPC regional contests and finals. The camp will consist of 7 ICPC-style contests and 2 days off.

Details

Participation fee for onsite participants is 150€ per person. It does not include regular meals, travel or accommodation. Some further details about location, travel and food options can be found on the website.

If you want to participate, but are unable to come onsite, we offer a reduced fee of 100€ per person for online participation. It is also possible to reduce fees individually if you are unable to attend some of the contests. This will be handled on a case-by-case basis.

We support and empathize with those affected by the ongoing war in Ukraine, therefore we offer a 100€ discount for affected individuals and teams affiliated with Ukrainian institutions. In other words, the fees would be 50€ and 0€ per person for onsite and online participation correspondingly.

The expected starting time for the contests is 10am CEST. For online participants, it is still a preferred starting time, but we will make accommodations for other starting times.

Most of our contests are fresh and developed for this camp. A small number of contests may be based on previous contests that have not been released to the general public. If you have seen some problems of a contest before, you can't participate on that day (and your participation fee will be reduced accordingly). We will privately contact participants who might be affected. Based on feedback, we will have a silence period until the end of November 2023, during which camp materials will not be released to the public. Therefore, we ask participants to not discuss the problems in public until that date.

Participants

If you are interested in participating, please fill the form here.

We ask you to register before September 8 if you want to participate online and before September 2 if you want to participate onsite.

Also, if your university or organization has a lively ICPC community that may be interested in attending the camp, and you have some contacts of people in charge (e.g. coaches) we would highly appreciate if you could fill the form here, so that we can send an invitation. Thanks!

Problemsetters

We'd like to thank and praise the authors of the contests in the camp, including:

• jeroenodb — Codeforces International Grandmaster, Computational geometry enjoyer. NWERC 2021 and 2022 bronze medalist.
• fwitt — POI silver medalist.
• Adam_GS — BOI 2023 winner, EJOI 2021 gold medalist, Codeforces International Grandmaster, problemsetter for OCPC 2023 winter.
• Asymmetry — IOI silver medalist, CEOI and BOI gold and two times POI gold medalist. CERC 2022 gold medalist.
• ppavic — triple IOI gold medalist.
• dorijanlendvaj — double IOI gold medalist, Codeforces Legendary Grandmaster.
• jtnydv25 — author of over 50 problems.
• Claris — ICPC 2017 and 2018 world finalist.
• -is-this-fft- — ICPC 2019 world finalist, Google Hash Code 2020 finalist.

...and others. We would also like to thank Um_nik and nor for their help with reviewing problem proposals.

You can find more details about contest rules and technical setup on the website.

Sponsors

Last but not least, we would like to say special thanks to our sponsors, who make the camp possible. If you are interested in sponsoring next editions of the camp or have any questions, please feel free to reach out at ocpc (at) mathos (dot) hr.

Finally, we would also like to thank Codeforces for guidance and promoting this announcement to the main page, eolymp for providing us an online judge for the contests and the Department of Mathematics at J. J. Strossmayer University of Osijek for all their organizational support and providing us a physical location to conduct the camp.