It's been a long day without you, Codeforces!

We are glad to invite you to take part in Codeforces Round 969 (Div. 2) and Codeforces Round 969 (Div. 1), which will start on Aug/30/2024 17:35 (Moscow time). You will be given 6 problems and 2 hours and 30 minutes to solve them in both divisions.

The problems are authored by LMydd0225, tzl_Dedicatus545, _FJqwq, Ternary_Tree_ and me wyrqwq and mostly prepared by LMydd0225. One of the problems is also prepared by DitaMirika.

We would like to thank:

• Artyom123 for his intelligent coordination, and for Russian translation.
• arvindf232, dXqwq, A_G, Atomic-Jellyfish, N_z__, Tony2_CF, abc864197532, PEIMUDA, hyman00, yuanruiqi, Imdie, _Purslane_, superyijin_txdy, SATSKY_2024target_IGM, Error_Yuan, WRKWRK, cfhj, Clan328, celin, Misuki, Romy67, misorin, yangchang, Fish_and_Chips, Yoav, turgon314, Tricopter, oloy, Lastiy124, Leonardo_Paes, flakes24, deneribeiro10, lhzawa for testing.
• MikeMirzayanov for Codeforces and Polygon platforms.

Hope you will enjoy the problems!

Score Distribution:

• Div. 2: $$$500 - 750 - 1000 - 1500 - 2250 - 2750$$$;
• Div. 1: $$$750 - 1250 - 1500 - 2000 - 2500 - 3000$$$.

badges$$$^\dagger$$$ of the authors:

$$$^\dagger$$$: Began in 2022 at NOI Shanghai, Badge Exchanging has been an activity popular among Chinese CPers. The host school for NOI 2022 decided to print badges containing the avatar of contestants for the contestants, and one can exchange his or her badge with another. The collection of one's badges (of other CPer's avatars) shows the group of CPers that he has met and even made friends offline. It has achieved great success. And since then, it has been a tradition for years.

UPD: Congratulations to the winners!

Div. 1:

1. tourist (Updated, and congrats!)
2. jiangly
3. ecnerwala
4. Radewoosh
5. Kevin114514

Div. 2:

1. mkrukov07
2. temp6
3. wjq1234567
4. bingpao
5. AuSquare (It seems that the rank 5 was banned? So let's move on to rank 6!)

The Editorial is out. You can also download Simplified Chinese Editorial in the contest material of the Div. 1 part of the contest.

Hello!

We are starting to test the long-awaited feature of non-rated registration for rounds. Here’s the plan: we will first test this feature in Testing Round 19 (Div. 3). Then, we will apply this innovation for ICPC-like rounds (Div. 4 Rounds, Div. 3 Rounds, Educational Rounds). After we have tested the feature in ICPC-like rounds, we will start using it in other types of rounds as well.

Here’s how the feature works:

• When you register for a round (if it is rated for you), you can choose non-rated registration if you do not expect to perform at your best (for example, if you might be interrupted during the round).
• You can change your registration type (rated or non-rated) BEFORE THE ROUND STARTS. Once the round starts, you cannot change your registration type.
• If you register for a round after it has started, you will automatically be registered as rated (if the round is rated for you). In other words, you will not be given the option to register as non-rated.
• After the round, the rating will be updated only for those who participated in the round and had a rated (regular) registration.

During the round, you will not be able to see whether another participant is registered as rated or non-rated. You will be able to find out later by checking if their rating has changed.

We urge you not to abuse this feature in the future and to try to participate in rated mode. Use this option only if you have a valid reason.

Let's test the new feature together: participate in Testing Round 19! We advise you to randomly choose your registration type so that we have both rated and non-rated registrations.

After the round, we will temporarily recalculate ratings to ensure everything works correctly. After that, of course, the rating changes from Testing Round 19 will be removed.

Thank you for participating!

UPD: Thank you all for testing! Share your feedback in the comments. The ratings for this round will be rolled back within a few hours.

(After 3 months) Hello again, Codeforces!

We are glad to invite you to participate in Codeforces Round 968 (Div. 2), which will start on Aug/25/2024 17:35 (Moscow time). You will be given 6 problems and 2 hours to solve them. Two problems are divided into two subtasks.

This round will be rated for participants whose rating is below 2100. Participants with higher rating can participate unofficially.

The problems were authored and prepared by me.

I would like to thank:

• 244mhq for perfect coordination.
• A_G, wutongchun, yeminghan for red testing.
• DisconnectedGraph, small_peter, JWRuixi for orange testing.
• yinhee, QwQwf, Jryno1, sinsop90 for purple testing.
• dieselhuang, WRuperD, CSQ31, gdf_yhm for blue testing.
• liujunyi123, Ender32k for cyan testing.
• ishaandas1 for green testing.
• Our previous testers Um_nik, antontrygubO_o, CharlieV, YuJiahe, Edwin__VanCleef for testing a subset of the problems.
• MikeMirzayanov for the great Codeforces and Polygon platforms.

• You

  for participating!

Scoring distribution: $$$500 - 750 - 1000 - (1000 - 1250) - (1750 - 1000) - 2500$$$.

Good luck & Have fun!

UPD1: Editorial and also Simplified Chinese Editorial are out.

UPD2: Congratulations to the winners!

Div. 2:

1. Empty_Dust
2. cz_yxx
3. Hosen_ba
4. farkon00
5. _minhduccp

Div. 1 + Div. 2:

1. jiangly
2. ksun48
3. kotatsugame
4. Sugar_fan
5. Golovanov399

UPDATE: Some time ago, there was news here that we supported C++23 by installing GCC 14 from the Winlibs project. It turned out that with this method of supporting C++23, some compatibility issues lead to significant performance drops in certain submissions. So, I tried another distribution for GCC 14: the MSYS2 project. It seems that this problem does not occur with it, and now there are no unexpected performance drops. Let's test this C++23 support option together!

Hello, Codeforces!

Together with Vladosiya, we've added support for the 64-bit g++14 C++23. You can find it under the name GNU G++23 14.2 (64 bit, msys2).

If you're using Windows, you can easily install it via our minimalistic package manager, PBOX, by running the command pbox install gcc14-64-msys2.

Thanks to the MSYS2 project! We used the distribution from the official package manager.

Your solutions will be compiled using the following command line: g++ -Wall -Wextra -Wconversion -static -DONLINE_JUDGE -Wl,--stack=268435456 -O2 -std=c++23 program.cpp -lstdc++exp.

Now you can start using C++23 features!

Please note that support for GNU G++23 14.2 (64 bit, msys2) is currently experimental. We invite you to join in the testing and experimentation process. Share your thoughts and experiences in the comments!

Hello Codeforces! (你好, Codeforces!)

Kaey and I are glad to invite you to Codeforces Round 967 (Div. 2) which will start on 20.08.2024 17:35 (Московское время).

The contest will last for 2 hours with 5 tasks for you to solve, and 1 task will have subtasks. The contest will only be rated for those with a rating not higher than 2099, but higher rated users are also more than welcome to participate out of competition. There is at least one interactive problem, so please read the guide for interactive problems if you are unfamiliar with them.

Holding the contest would have been impossible without the help from:

• Kaey for supercalifragilisticexpialidocious coordination.
• feecle6418 for providing idea of one of the problem.
• BurnedChicken, cheissmart, SorahISA, WiwiHo, Fysty, Potassium, Emilan, Wayne_Yan, sam571128, Darren0724, HNO2, FoodSheep, Aestivate, jamesbamber, franv, jakao, warner1129, guagua0407, ub33, Bossusuprem, AverageAmogusEnjoyer, _hq8398_, XDEv11, Qualified, temmieowo, kenkenken, ayhan23, DanielMontes, TLE_Automaton, Mohamed_M.M.R, BaoCoder613, alls, Vamperox, Ahmad_OS, AdunAdunov, ciao_gio, baibaiouo, VelajZmaj, pandaa73 for testing and giving useful feedback to make the round better.
• Alexdat2000 for translating the statements to Russian.
• MikeMirzayanov for Codeforces and Polygon.

The score distribution is $$$500 - 1000 - 1500 - 2000 - (2000 - 2000)$$$.

Good luck and have fun!

UPD1: Editorial

UPD2:

Congratulations to the winners:

Div.1 + Div.2:

1. maspy
2. Mangooste
3. kotatsugame
4. Rubikun
5. potato167

Div.2:

1. kkkksc03
2. ThMinh_
3. yifeizhu
4. activedeltorre
5. suuuuuu

Привет, Codeforces!

Благодаря поддержке Neapolis University Pafos, продолжается серия образовательных раундов. Университет предлагает получение степени бакалавра в области компьютерных наук и искусственного интеллекта со стипендиями JetBrains. Получите передовые навыки в области искусственного интеллекта и машинного обучения, которые подготовят вас к востребованным техническим карьерам. Любопытно? Ознакомьтесь с учебной программой прямо сейчас. Доступно ограниченное количество стипендий. Не упустите свой шанс учиться в Европе бесплатно!

В 15.08.2024 17:35 (Московское время) состоится Educational Codeforces Round 169 (Rated for Div. 2).

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, Иван BledDest Андросов и Максим Neon Мещеряков. Также большое спасибо Михаилу MikeMirzayanov Мирзаянову за системы Polygon и Codeforces.

Данный раунд частично пересекается по задачам с личным соревнованием летней школы Саратов-2024. Если вы участвовали в этом соревновании, то воздержитесь от участия в раунде.

Удачи в раунде! Успешных решений!

UPD: Разбор опубликован

Привет! В 13.08.2024 17:40 (Московское время) начнётся Codeforces Round 966 (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, после её завершения все успешные попытки будут перетестированы на успешных взломах. 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 6-8 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, Gornak40, senjougaharin и Vladosiya.

Также большое спасибо:

1. MikeMirzayanov за помощь с идеями и системы Polygon и Codeforces.

2. FairyWinx, TheScrasse, Be_dos за красное тестирование раунда.

3. irkstepanov, Kirkon, ikrpprppp, Kaey, Bruteforceman за жёлтое тестирование раунда.

4. Vitaly503, FBI за фиолетовое тестирование раунда.

5. satyam343, vikram108 за синее тестирование раунда.

6. trgt26 за зелёное тестирование раунда.

Всем удачи!

UPD: Разбор опубликован.

Привет, Codeforces!

Мы рады пригласить вас на EPIC Institute of Technology Round August 2024 (Div. 1 + Div. 2), который состоится в 11.08.2024 17:35 (Московское время).

Задачи подготовлены Flamire, le0n и xcyle. Вам будет дано 8 задач и 3 часа на их решение. Две задачи разделены на две подзадачи. Раунд будет рейтинговым для всех.

Мы бы хотели поблагодарить всех, кто помогал нам в подготовке этого раунда:

• TheScrasse за его блестящую координацию.
• AdunAdunov и Alexdat2000 за перевод на русский язык.
• orzdevinwang, arvindf232, MagicalFlower, rui_er, LipArcanjo, zhaohaikun, Mr_Wu, lambert0704, acniu, wenhao801, using233, Kaey, DeadlyCritic, _RedWine_, Bossusuprem, Hihihah, FzArK, MatteoArcari, Vamperox, songhongyi, AdunAdunov за тестирование раунда и полезные отзывы.
• MikeMirzayanov за Codeforces и Polygon.

Разбалловка задач: 500 - 750 - 1000 - (1000 - 1000) - 2000 - (2000 - 1250) - 4000 - 6000

Всем удачи!

Наши поздравления победителям!

1. jiangly
2. Radewoosh
3. Benq
4. Um_nik
5. maspy

Разбор доступен в виде pdf и будет опубликован отдельно завтра.

А теперь несколько слов от сегодняшнего спонсора!

About EPIC Institute of Technology

EPIC Institute of Technology is an innovative educational project, driven by the Deltix team under the EPAM Systems umbrella. As part of EPIC — EPAM Product Innovation Center, we aim to cultivate the brightest minds and prepare them for a future in cutting-edge technology projects.

Why EPIC:

EPIC Institute of Technology is an accelerator for the best talents. Our students will acquire hands-on experience in one of the selected major programs, all of which are highly demanded right now on top projects, together with the fundamental knowledge, so indispensable for real professionals. Successful graduates will have a unique chance to jumpstart their career on the most challenging and interesting EPAM projects worldwide. You will join the community of intelligent and driven individuals and have an honor to work with and learn from them.

Here are the answers to the most common questions:

How much does education cost?

EPIC Institute of Technology is completely free. There are no fees to register for exams, tuition fees or any other hidden liabilities. The only restriction for getting into EPIC Institute of Technology is age. You must be older than 18 years old to become a student.

How is the educational process organized?

Each program lasts exactly one year. The academic year consists of two semesters. Courses in the first semester are the same for all programs. Courses in the second semester depend on the selected major program.

During the semester, students complete homework assignments and take 2 exams—a midterm and a final. The final grade a student gets for each training course depends on the quality of completed assignments and participation in practical classes.

How will the classes be held?

Lectures will be pre-recorded and available for self-study. Practical classes will be held at the specified time according to the provided schedule. Also, students will have an access to a Discord server, where they can discuss topics of academic interest with teachers and other students.

In what language will I study?

All programs are in English.

How can I apply?

The admissions process is as follows:

1. Fill out the form on the website.

2. Take part in one of the entrance exams that will be held in our Codeforces group. You can also find past exam breakdowns there, which may help you in your preparation. Exam dates will be announced later, so stay tuned to the announcement channel and our LinkedIn group.

3. If you successfully pass the exam, you will receive an invitation email.

What will happen after graduation?

All EPIC Institute of Technology graduates will get a diploma and the best students will be offered to join, either as an intern or a full-time position, one of the hot EPAM projects where skills acquired at EPIC Institute of Technology will be demanded.

Please visit our website to learn more about EPIC Institute of Technology and the available programs. If you have any questions, you can quickly ask them in our chat.

Wazzup Codeforcers!

sum, satyam343, and I are extremely ecstatic to invite you to Codeforces Round 965 (Div. 2) on Aug/10/2024 17:35 (Moscow time). You will be given 5 problems and 2 hours to solve them. 1 problem will have subtasks. This round will be rated for all participants with rating below 2100. We spent the most time cooking up this round than any other round, so it means a lot if you will participate.

We would like to orz the following individuals for making the contest possible:

• Our coordinatorz satyam343 for his gracious coordination and donation of his own problems to this contest.

• Our testuwuers: Benq, omeganot, maxwellzen, 244mhq, null_awe, Dominater069, A_G, Yam, IceKnight1093, Phi-001, CSQ31, fishy15, Java, kingmessi, Pols_Agyi_Pols, harsh__h, awesomeguy856, tyr0Whiz, andrewtam, oursaco, 18o3, lethan3, Stefan2417, milind0110, willy108, amsraman, MridulAhi, AryRDW, h2rsh, page_fault, IceWolf898, US3RN4M3, callmepandey, jay_jayjay, flight, xug, Qualified, Sacharlemagne, chromate00, ntarsis30, redpanda, Faizal, windreaper, yash_9a3b, Prady, Non-origination, waidenf, ETL, oddvalue, and Rahuldeb5.

• Alexdat2000 for translating the statements to Russian.

• MikeMirzayanov for developing Codeforces and Polygon (mentioning this so I don't lose 1000 social credits).

Score Distribution: $$$500 - 750 - 1250 - 1500 - (1750 + 1750)$$$

UPD: We know there has been a lot of disapproval for problem C. We're sorry for it. Please view https://codeforces.net/blog/entry/132507

UPD: Editorial

Hello Codeforces!

flamestorm, mesanu and I want to invite you to Codeforces Round 964 (Div. 4).

It starts on Aug/06/2024 17:35 (Moscow time).

The format of the event will be identical to Div. 3 rounds:

• 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).

Additionally, there might be problems that are interactive, so please read the guide of interactive problems before the contest.

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 behaviour. 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: Dominater069, Qualified, Vladosiya, qwexd, Gheal, cry, haochenkang.

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

Good Luck!

UPD: Editorial is out!