Hello Codeforces!

SlavicG, mesanu, MikeMirzayanov, Errichto, and I welcome you to Codeforces Round 790 (Div. 4). It starts on May/10/2022 17:45 (Moscow time).

The format of the event will be the same as before:

• 5-8 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 (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth 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 fourth 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 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: timreizin, magnus.hegdahl, Adam_GS, KrowSavcik, qwexd, pseudocoder10, jampm, Neophiliatic, Codula and of course _Vanilla_.

We suggest reading all of the problems and hope you will find them interesting!

Good luck!

UPD: the start of the round is delayed by 10 minutes.

UPD: Editorial is published!

Hello, Codeforces! ฅ(*`ω´*)ฅ

We are glad to invite you to take part in Codeforces Round 789 (Div. 1) and Codeforces Round 789 (Div. 2), which will be held on 08.05.2022 17:35 (Московское время).

The round will be rated for all participants from both divisions. Participants in each division will be offered 6 problems and 2 hours to solve them. Both divisions will share 4 problems.

The problems were written and prepared by funer, dark_light, FreshP_0325, Frank_DD, qsmcgogo, winterzz1, Sugar_fan, TomiokapEace and me.

Thank to:

• 74TrAkToR for excellent coordination of this round! And translating the statements to Russian.

• KAN for helping us to review and fix some statements.

• TomiokapEace for helping us to translate all the statements and tutorials to English.

• Sugar_fan for giving valuable advice and helping us to fix some statements.

• Elder_Giang, ddytxdy, zwezdinv, zarubin, olyazyryanova, marzipan, MichsSS, playf, TeaTime, gojira, plagues, AlexLuchianov, kpw29, Huah, Yzm007, Duck_sajin, Operation27, Venn, Nephry, Sugar_fan, errorgorn, Um_nik, TadijaSebez, Prokhor08, Grigoreva-Irina, Dragonado, lunaTu and jqdai0815 for testing this round and giving good advice.

• MikeMirzayanov and his Codeforces team for amazing systems Codeforces and Polygon!

• NEAR for supporting this round, details can be found in this post.

Here are some things I personally want to say. This is my second round. Three years have passed since the first round round 573 I held. Now I have graduated and worked. I like codeforces very much. Though I have already participated in work, haven't trained for a long time, my ability has degraded a lot, I will still come to codeforces to participate in the contest in my spare time. This time I also prepared some problems to propose a round, but for some reasons, most of them were rejected. In particular, one of my favorite problems was rejected because "many testers don't like it". I'm a little frustrated, but I also understand that the coordinator's job is to make the round better and more people like this round. I think it's a great honor to prepare round on codeforces and let so many people around the world try to solve the problem I prepared. I will accumulate some more interesting ideas for the next round and try to make more people like the problems I prepared.

I'd like to express my great gratitude to my friends for preparing this round with me, I don't think I can prepare this round alone without them. I really appreciate having the support of my good friends in my round.

In addition, the three naughty cats mentioned in the statement.(*=｀ω´=)ﾉ I understand that I shouldn't post pictures irrelevant to the statement, so I post it here ↓

Finally, I hope you like the problems in this round, good luck and have fun!(≧ω≦)/

The score distribution will soon be published.

UPD1: Although our coordinator allows to post the PDF of Chinese statements in the contest material, it seems that codeforces does not allow it. We are only allowed to post something after the round. So we will still post Chinese tutorials after the round.

UPD2: List of contributors is a bit changed, and the score distribution will be:

• Div.2: 500 — (750 + 1000) — 1250 — 2000 — 2000 — 2750

• Div.1: 500 — 1250 — 1250 — 2000 — 2500 — 3500

UPD3: Note that the score of the last problem of Div.1 has changed, 4000 → 3500.

UPD4: Editorial is out, and Chinese Tutorial will soon be published.

UPD5: Chinese Tutorial is out.

UPD6: Congratulations to the winners!

Div.1:

1. maroonrk

2. tourist

3. eecs

4. ainta

5. duality

Div.2:

1. NiNiV

2. WA_On_Pretest2_Forces

3. ouql

4. KroosTheKeenGlint

5. jialiang250

I'm glad to invite you to Codeforces Round 788 (Div. 2), which will be held on May/06/2022 17:35 (Moscow time).

This round is rated for the participants with rating lower than 2100.

You will be given 6 problems and 2 hours to solve them. All problems were prepared by me, Hemose and ZerooCool.

I would like to thank:

• Monogon, for a lot of things (awesome coordination, helping in preparation, rejecting only not interesting tasks and a lot of useful discussions).

• I_Love_Slim for teaching us BLABIZO useful concepts.

• Our army of testers YahiaSherif, TripleM5da, TheScrasse, Bakry, IsaacMoris, TeaTime, magnus.hegdahl, generic_placeholder_name, NemanjaSo2005, Abdelrahman_Etman, TheSawan, gojira, Priyam2k, Urvuk3, Menna-Allah05, Khater.

• MikeMirzayanov, for the amazing Codeforces and Polygon platforms.

• NEAR for supporting this round, details can be found in this post.

The statements are short and we have tried to make the pretests strong. I encourage you to read all the problems.

For people who don't like stories, you will find all the stories written in italic you can skip them safely.

We are sincerely looking forward to your participation. We hope everyone will enjoy it.

Good luck and see you in the standings!

UPD: The score distribution is 500-1000-1750-2250-2750-3000.

UPD: We hope you liked the problems, here is the Editorial

Привет! В 05.05.2022 17:35 (Московское время) начнётся Codeforces Round 787 (Div. 3) — очередной Codeforces раунд для третьего дивизиона. В этом раунде будет 6-7 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 6-7 задач и 2 часа 15 минут на их решение.

Штраф за неверную попытку в этом раунде (и последующих Div. 3 раундах) 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.

Спасибо MikeMirzayanov за платформы, помощь с идеями для задач и координацией нашей работы. Задачи были придуманы и написаны командой Университета ИТМО: MikeMirzayanov, MisterGu, myav, Gol_D, Aris, senjougaharin, мной Vladosiya.

Также большое спасибо avevad, yorky, UncleSema, vsinitsynav, GoracioNewport, Tvorozh0k, any_nickname, I.AM.THE.WILL и Jostic11 за тестирование раунда и весьма полезные замечания.

Всем удачи!

UPD:Разбор

Привет! В 02.05.2022 17:35 (Московское время) начнётся Codeforces Round 786 (Div. 3) — очередной Codeforces раунд для третьего дивизиона. В этом раунде будет 6 или 7 задач (или 8), 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. Вам будет предложено 6 или 7 (или 8) задач и 2 часа на их решение.

Штраф за неверную попытку в этом раунде (и последующих Div. 3 раундах) 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 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.

Задачи вместе со мной придумывали и готовили Адилбек adedalic Далабаев, Александр fcspartakm Фролов, Иван BledDest Андросов и Михаил awoo Пикляев. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Также спасибо ashmelev, Vladosiya, mesanu и I.AM.THE.WILL за тестирование раунда и полезный фидбек по задачам!

Удачи!

UPD: Обратите внимание, что задачи раунда частично пересекаются с задачами Внутривузовской олимпиады Саратовского ГУ по программированию. Если вы участвовали в олимпиаде, то воздержитесь от участия в раунде.

UPD2: Разбор опубликован!

Hello Codeforces,

I invite you to participate in Codeforces Round 785 (Div. 2) which will be held on 30.04.2022 17:35 (Московское время). The round will be rated for participants of Division 2 with rating strictly less than 2100. But as always, the participants of Division 1 are welcome to take part out of competition.

You will be given 6 problems and 2 hours to solve them. Moreover, there will be atleast $$$1$$$ and atmost $$$1048576$$$ interactive problems. So, you are advised to refer to the guide on interactive problems in case you are not familiar with them.

I would like to thank the following people for their contribution to the round:

• Artyom123 for his amazing coordination, helping me throughout the preparation of the round and translating the statements.
• Um_nik, Monogon, kclee2172, TheScrasse, yash_daga, Sad_reacts_only, AlperenT, Utkarsh.25dec, abhidot, PR_0202, towrist, Rubalien, hritik31, snowysecret, alok_k6618 and harsh2804 for testing the round and providing their feedback.
• MikeMirzayanov for the great Codeforces and Polygon platforms.
• NEAR for supporting this round, details can be found in this post.
• You for participating.

This will be my second Codeforces round and based on the feedback by participants on Round #730, I have implemented the following changes:

• The round will have no theme. I have tried to keep the problem statements as short and to the point as possible.
• The pretests have been made stronger (specifically, more pretests have been included).
• I have tried to keep the samples and their explanation as useful as possible.
• No floating-point precision issues this time.
• The I/O constraints for the interactive problem(s) have been kept low to provide a fair ground to the languages with slower I/O.

The score distribution will be released strictly before the round and the editorial will be released strictly after the round.

Good luck and have fun!

UPD: The score distribution is $$$500-750-1500-2000-2750-3250$$$.

UPD: Editorial

UPD: Congratulations to the winners

Div. 1 + Div. 2 -

1. ksun48
2. Kirill22
3. JiBaDa
4. Geothermal
5. errorgorn

Div. 2 -

1. JiBaDa
2. A-SOUL_Ava
3. Beduardo
4. happy-potato
5. Moomer

First solves -

На официальном сайте Летней школы по компьютерным наукам открылся прием заявок. Школу для учеников 8-10 классов проводит факультет компьютерных наук НИУ ВШЭ совместно с центром поддержки одарённых детей “Стратегия” в Липецке. Отбор участников пройдёт в несколько туров, первый из которых пройдёт 15-16 мая.

С 16 по 30 июля 2022 года Летняя школа по компьютерным наукам примет у себя талантливых школьников из 8-10 классов, желающих добиться высоких успехов в олимпиадах по информатике. Как и раньше, школу организует ФКН ВШЭ совместно с центром поддержки одарённых детей “Стратегия” в Липецке.

Обучение в школе будет проходить в четырёх параллелях: C, B', B и A в соответствии с классом обучения в школе и уровнем подготовки участника. Основное внимание будет уделяться изучению алгоритмов, используемых при решении олимпиадных задач.

Желающим принять участие в ЛШКН-2022 нужно заполнить регистрационную анкету и решить вступительные задания той параллели, в которой они хотят учиться, первый отборочный тур пройдёт с 08:00 15 мая по 22:00 16 мая по московскому времени. Всем заполнившим анкету на указанный электронный адрес будет высылаться информация об отборе в школу.

Hello, Codeforces!

We are thrilled to announce the dates of our annual online programming competition, the SIT & JUB STAR Contest 2022, organized by the Schaffhausen Institute of Technology (SIT) in Switzerland and our partner Jacobs University Bremen (JUB) in Germany.

Winners will have the chance to receive exciting prizes, including a full scholarship for Master in Computer Science and Software Engineering program.

What is the SIT & JUB STAR Contest?

The goal of the SIT & JUB STAR Contest is to promote interest in the field of Computer Science and Software Engineering, giving participants an opportunity to demonstrate their knowledge of programming. It is also a winning ticket for full scholarship to a master program. To participate, click here.

The SIT & JUB STAR Contest 2022 timetable

April 16 15:00 (UTC), 2022 | Practice Round: An opportunity to familiarize yourself with the testing environment. You can practice any time from April 16 to 5 minutes before the Final Round. This is an optional step but we highly recommend taking part in it. The results of this round will not affect your final score.

April 26 08:00 (UTC), 2022 | SIT & JUB STAR Contest: The contest starts at 8 am, UTC, on April 26. You have 4 hours to complete all requested tasks, which include 8 to 12 problems of various levels of difficulty in algorithmic programming.

DATES | Interview Round and Winner Announcements: Participants with the highest scores will be invited for the interview round with professors from SIT and Jacobs University Bremen. Winners will be notified by email.

Prizes

Several prizes are offered to the top candidates:

• Full scholarships for the Master in Computer Science and Software Engineer program offered in Switzerland and Germany
• Other scholarship options available
• Some exciting gifts from Switzerland and Germany!

Who can participate?

Everyone is welcome! The contest is open for all ages and skill levels, all you need is a passion for coding.

To be eligible to win the full scholarship, please consult the following guidelines.

How can I participate?

• Fill out the contest registration form here.
• Register at Codeforces using a special link you will receive in the confirmation email. Please fill in the same email address you used in the registration form.
• If you have any further queries, please reach out to [email protected]

About the Master in Computer Science and Software Engineering

Our 2-year hybrid Master in Computer Science and Software Engineer brings the latest must-knows in science, tech and business, through lively lectures by renowned field leaders and hands-on lab activities. With this program, go from studying in Schaffhausen in Switzerland, known for its excellence in IT science and technology, to Bremen in Germany, a vibrant campus for English-speaking students, with a rich academic tradition. Click here to learn more.

About SIT and Jacobs University Bremen

SIT is a global institution dedicated to promoting Science, Education and Technology. Headquartered in Schaffhausen, Switzerland, SIT is a growing ecosystem comprised of a non-profit component, with education and research, as well as commercial technology spin-offs, consulting services, a start-up incubator and investment funds.

Thanks to its two English-language campuses – in Bremen, Germany and in Schaffhausen, Switzerland – SIT offers interdisciplinary university programs to students from around the globe with flexible learning models. With a research-centric approach and an entrepreneurial mentality at its core, the SIT education ecosystem is a gateway to the next generation of digital leaders.

We look forward to seeing you show off your programming skills on competition day.

Good luck!

The Southwestern Europe Regional Contest will take place on the 23rd of April. It is the ICPC regional contest (i.e., the winning teams will advance to the ICPC World Finals) for teams from France, Israel, Italy, Portugal, Spain, and Switzerland.

The mirror contest SWERC 2021-2022 - Online Mirror (Unrated, ICPC Rules, Teams Preferred) will be held on Codeforces at Apr/24/2022 14:05 (Moscow time) and will last 5 hours.

The mirror contest will contain all the problems from the official competition plus some additional problems.

I am the chief judge for the competition and I want to thank:

• The amazing set of judges who proposed and prepared the problems: cescmentation_folch, cip999, Delfad0r, gangsterveggies, Giove, gog.gerard, majk, Petr, Simon, tap_tapii.
• The MIT team composed of Rewinding, TLE, antontrygubO_o for testing the round and Philae for proofreading the statements.
• Everyone involved in the organization of SWERC, in particular Dariost (director), edomora97 (technical director), Gianpaolo Agosta (director) and wil93 (secretary).
• MikeMirzayanov for Polygon (that we used to prepare the problems) and for letting us host the mirror on Codeforces.

I invite you to participate in the contest and I hope that you will like the problems.

On the difficulty
The contest features problems with difficulties from div2A to div1F; so anyone can find something at their level.

Many teams without much experience participate in SWERC, so the problem set should be enjoyable also for div2 contestants. On the other hand, solving all the problems should be challenging even for the strongest teams in the world: the MIT team did not AK in 5 hours.

How did you manage to get such good quality of the problems...
Who are the setters?
One of the best problem sets I have seen if not best

Rules

1. The contest is unrated, so your codeforces rating will not be affected.
2. The scoring is ICPC-style: teams are first sorted by number of problems solved, then the time-penalty is used as a tie-break. An incorrect submission gives a 20 minutes penalty.
3. We encourage participation as a team.
4. If you are participating in a team, we encourage you to use only one computer for coding the solutions (as in an ICPC contest). Regarding using templates and copy-pasting code: feel free to do it.

UPDATE: We hope you liked the problems, here is the editorial for all the problems in the mirror: https://codeforces.com/blog/entry/102042 .

UPDATE: Congratulatins to the all the participants of the onsite contest and in particular to the two gold medal winning teams, both solving 10 problems (and with a very similar penalty time):

1. Raw Pots -- Harbour.Space University
2. TAU++ -- Tel Aviv University

And congratulations also to the four teams who managed to solve all the problems in the mirror:

1. tourist, ksun48
2. jiangly
3. Merkurev, KAN, Um_nik
4. djq_cpp, hehezhou, jqdai0815

On Apr/23/2022 17:05 (Moscow time), we will host Codeforces Global Round 20.

Note the unusual timing, it is 30 minutes earlier.

This is the second round of the 2022 series of Codeforces Global Rounds. The rounds are open and rated for everybody.

The prizes for this round:

• 30 best participants get a t-shirt.
• 20 t-shirts are randomly distributed among those with ranks between 31 and 500, inclusive.

The prizes for the 6-round series in 2022:

• In each round top-100 participants get points according to the table.
• The final result for each participant is equal to the sum of points he gets in the four rounds he placed the highest.
• The best 20 participants over all series get sweatshirts and place certificates.

Thanks to XTX, which in 2022 supported the global rounds initiaitive!

All problems were written and prepared by errorgorn, maomao90 and oolimry.

We would like to thank the following people who made this round possible:

• antontrygubO_o for coordinating our round and somehow only rejecting 2 div2As.
• oolimry for contributing to national defence and keeping Singapore safe.
• dario2994 for being the best tester. The perfect tester does not exist but I think dario2994 comes really close to it.
• tqbfjotld, gamegame,dorijanlendvaj, dario2994, kclee2172, Monogon, nvmdava, TheScrasse, jamessngg, pavement, iLoveIOI, AlperenT, icypiggy, timreizin, Myrcella, DeMen100ns, QuangBuiCPP, bWayne, chicken337, joelau for testing the round and providing useful feedback.
• MikeMirzayanov for Codeforces and Polygon.

You will have 3 hours to solve 9 problems, one of which is divided into two subtasks.

The scoring distribution is 250-500-750-1000-1500-(1250+1250)-2750-3000-4000. GLHF!

Also, please upvote the blog so that I can get more contribution than antontrygubO_o.

PS: We would like to take this opportunity to congratulate rotavirus or antontrygubX_y on getting married. Wishing you lots of love and happiness.

Edit: Editorial is released. Even if you have solved a problem, we encourage you to read the editorial as you might learn something new from it.