Hello, Codeforces!

I, along with AlperenT, Ari, BucketPotato, ScarletS, and ToxicPie9, would like to invite everyone on Codeforces to the April Fools Day Contest 2023! The 11th April Fools Day Contest will take place on Apr/01/2023 17:35 (Moscow time). This is a joke competition in which solving the problem is often easier than figuring out what the actual task is.

Please note that the round is unrated.

In this round you'll be given $$$n$$$ weird problems and 2 hours to solve them, where $$$7 \leq n \leq 12$$$. At most $$$\sqrt{n}$$$ of the problems will be interactive. The contest will use ACM ICPC rules (no hacks, the standings are decided by the number of solved problems and penalty time earned on them).

You can submit solutions in any language allowed by Codeforces, unless the problem says otherwise. To get an idea of what the contest will look like, you can check out the contests of the past years: 2012, 2013, 2014, 2016, 2017, 2018, 2019, 2020, 2021, 2022.

Good luck, and have fun!

UPD1: Thanks willy108 for testing!

UPD2: The editorial is released!

UPD3: Congrats to the winners!

1. InternetPerson10
2. Geothermal
3. A_G
4. Maksim1744
5. LJC00118

And congrats to the first solvers!

• A: zscoder
• B: KeNaj712
• C: conqueror_of_tourist
• D: namcartoon06
• E: SanguineChameleon
• F: A_G
• G: lethan3
• H: InternetPerson10
• I: aberent (the only person who solved it in contest!)
• J: mxdcxt

UPD4: Sorry for the inconvenience, the contest is now open for practice submissions + virtuals.

Hello, Codeforces!

I'm very glad to invite you to participate in CodeTON Round 4 (Div. 1 + Div. 2, Rated, Prizes!), which will start on 31.03.2023 17:35 (Московское время).You will be given 8 problems and 2 hours to solve them. The round will be rated for everyone.

I'd like to give my sincere thanks to:

• 74TrAkToR for the wonderful coordination!

• Sulfox for the help with the statements.

• Suika_predator, SSerxhs, apeiya, xay5421, NemanjaSo2005, applese, bxhnb, fr200110217102, Sulfox, DF_3Mz PaperCloud, CedeaT0, Kath1031, jcccc, dyxg, tzc_wk, xiaoziya, qiqi20021026, Pointy, HorizonWind, ilyakrasnovv, ShmilyTY, njupt_lyy, rsj,hzr, p_b_p_b, ak2006, flakes24, Milesian, pb0207, _Vanilla_, Lavine, alwyn and MagicalFlower for testing the round.

• MikeMirzayanov for the great codeforces and polygon platform.

• You for take part in the round.

Hope everyone can enjoy the round!

UPD: The tutorial is here.

And here is the information from our title sponsor:

Hello, Codeforces!

We, the TON Foundation team, are pleased to support CodeTON Round 4.

The Open Network (TON) is a fully decentralized layer-1 blockchain designed to onboard billions of users to Web3.

Since July 2022, we have been supporting Codeforces as a title sponsor. This round is another way for us to contribute to the development of the community.

The winners of CodeTON Round 4 will receive valuable prizes.

The first 1,023 participants will receive prizes in TON cryptocurrency:

• 1st place: 1,024 TON
• 2–3 places: 512 TON each
• 4–7 places: 256 TON each
• 8–15 places: 128 TON each
• …
• 512–1,023 places: 2 TON each

We wish you good luck at CodeTON Round 4 and hope you enjoy the contest!

Greetings Codeforces community!

We are excited to announce the Constructor Open Cup 2023, our annual online programming competition organized by Constructor University and JetBrains.

What is the Constructor Open Cup 2023?

Constructor Open Cup is an online contest organized by Constructor University and JetBrains, the global leading tool provider for developers, to promote interest in computer science, data science, software development, and software engineering. You'll have to race against the clock to solve real-life programming challenges.

Put your knowledge and skills to the test in this 4-hour competition and stand a chance to walk away with a scholarship for the Bachelor's degree in Data Science and Software Development at Constructor University, Germany’s #1 private university*!

Constructor Open Cup timetable

• March 23-29, 2023 | Practice Round

Get familiar with the testing environment during this practice round. We highly recommend this optional step. Don’t worry: it won’t affect your final score!

• March 30, 2023 at 2 PM (UTC) | Main Round

You will have 4 hours to complete a series of algorithmic programming tasks of various difficulty levels.

Registration closes 1 hour before the start of the contest.

Prizes and Winner Announcement

The top candidates will receive exciting prizes, including:

• Chance to get scholarships for the Bachelor’s degree in Data Science and Software Development*
• Exciting memorable gifts from Constructor University and JetBrains

We're looking forward to seeing your programming skills on competition day, and we wish you the best of luck.

*The winners who applied to the BSc program in Data Science and Software Development will receive an email to schedule the interview with Constructor University professors and JetBrains.

Can I participate?

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

To get the chance for the JetBrains scholarship for Data Science and Software Development program, please check Constructor University’s eligibility requirements.

How can I participate?

• Register your details here.
• Register at Codeforces using the Login/Password you receive in the confirmation email.
• If you have any further queries, please reach out to [email protected].

Why should I join the Constructor Open Cup?

Previously known as ‘STAR Contest’, the competition attracted more than 1,600 contestants across 82 countries over the past three years. Renamed to Constructor Open Cup in 2023, this contest welcomes all regardless of age, qualifications, or skill level.

By participating in the Constructor Open Cup, you will:

• Get recognized by top science and technology leaders
• Pit your algorithmic problem-solving skills against competitors from other countries
• Get a chance to get a full scholarship for BSc program in Data Science and Software Development

Don't miss out on this exciting opportunity to challenge yourself and showcase your talents. Join the Constructor Open Cup today!

About the BSc Data Science and Software Development program

This program prepares talents to become tomorrow’s elites in software development, programming languages, data analysis, and machine learning. You will benefit from the latest insights and knowledge from top industry partners and get the right skills needed for these rapidly changing industries. Through real-world projects, the practice of the latest technologies, and the close mentoring of industry experts, you will gain a unique experience that sets you up for successful career opportunities. Learn more about the program here.

About Constructor University

Founded in 2001 as a private, English-language campus university, it repeatedly achieves top results in national and international university rankings. Its more than 1,600 students come from over 110 countries, and around 80 percent have moved to Germany to study. Research projects at the University are funded by the German Research Foundation, the European Union's Framework Program for Research and Innovation, and global leading companies.

About JetBrains

JetBrains creates intelligent software development tools used by over 15.9 million professionals and 90 Fortune Global Top100 companies. Its lineup of more than 30 products includes IDEs for most programming languages and technologies, such as IntelliJ IDEA, PyCharm, and others, as well as products for team collaboration, like JetBrains Space. JetBrains is also known for creating the Kotlin programming language, recognized by Google as the preferred language for Android development. The company is headquartered in Prague, Czech Republic, and has offices throughout the world. For more information, please visit https://www.jetbrains.com/

Hello, Codeforces!

I am very glad to invite you to the Codeforces Round #861 (Div. 2), which will take place in Mar/29/2023 12:05 (Moscow time). This round will be rated for the participants with rating lower than 2100.

My sincere thanks to:

• KAN и Aleks5d for the great coordination of this round!

• Wind_Eagle, BaluconisTima, kartel, gepardo and 244mhq for the tasks ideas, and also BaluconisTima, 244mhq, VEGAnn, Vladik and andrew for preparing the tasks.

• vilcheuski and programmer228 the rest of the author team, without whom this round would not have happened.

• BaluconisTima for the splendacious pictures, which complement each problem.

• MikeMirzayanov for Codeforces and Polygon platforms.

• You for participating in this round.

You will have 2 hours and 30 minutes for solving 6 tasks, one of which will be divided into easy and hard verions. The round is based on the problems from the Belarusian National Olympiad. We kindly ask all Belarusian students who participated in this olympiad, to refrain from taking part in this round and discussing the problems publicly before the round ends.

I hope you will enjoy the round!

Round testers (will be available later): Ormlis, 4qqqq, nnv-nick, olya.masaeva, Makcum888.

Preliminary score distribution: 750-1000-1500-2000-2500-3250.

UPD: the round was rebalanced. You will have 2 hours for solving 5 tasks, one of which will be divided into easy, medium and hard verions.

Score distribution: 750-1000-1500-1750-(1750+1000+750).

Editorial: https://codeforces.com/blog/entry/114523

Winners:

Div. 1 + Div. 2:

1) BurnedChicken

2) maspy

3) happylmb

Div. 2:

1) happylmb

2) Cherished

3) 2021_yes

Hello Codeforces!

I am happy to invite you to Codeforces Round 860 (Div. 2), which will be held on Mar/26/2023 17:35 (Moscow time).

This round will be rated for participants with rating lower than 2100. Participants with a higher rating are invited to participate in the round unofficially.

You will be given 6 problems and 120 minutes to solve them. All problems were authored and prepared by me.

The traditional thanks-list to everyone who took part in the creation of the round:

🤴 DishonoredRighteous for coordinating the round

🐞 gyh20 for black-red testing of the round

😈 feecIe6418, iakovlev.zakhar, Dart-Xeyter, Adam_GS, ShuiLaoshi, golikovnik, Gary2005 for red testing of the round

🐫 NemanjaSo2005, Alexdat2000, Kon567889, tem_shett for orange testing of the round

👾 SlavicG, Psychotic_D for purple testing of the round

🐳 C2A, Masha237, ayhan23, Khonshu08, Brahma_tet for blue testing of the round

👽 Lord_David for green testing of the round

🦄 mejiamejia for help with testers for the round

🤡 sevlll777 for the problem, without which the round would be unbalanced, and the problems that were not included in the final problemset

🎅 MikeMirzayanov for the amazing Codeforces and Polygon platforms
ㅤㅤㅤㅤ

I sincerely hope that you will find the problems interesting and you will enjoy solving them. Good luck!

Score Distribution:

500 — 750 — 1250 — 1750 — 2250 — 3000

UPD: Editorial

UPD2: Congrats CHAMPIONS!

Unofficially:

1. jiangly

2. A_G

3. neal

4. maspy

5. turmax

Officially:

1. satyam343

2. Sunnatov

3. RGB_ICPC7

4. amirhoseinfar1385

5. vbgladkikh

First AC:

A: nifek

B: AHappyPotato

C: AHappyPotato

D: aryan12

E: lebowski998

F: zihouzhong

Hello Codeforces!

On Mar/23/2023 17:35 (Moscow time) Educational Codeforces Round 145 (Rated for Div. 2) will start.

Series of Educational Rounds continue being held as Harbour.Space University initiative! You can read the details about the cooperation between Harbour.Space University and Codeforces in the blog post.

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 or 7 problems and 2 hours to solve them.

The problems were invented and prepared by Adilbek adedalic Dalabaev, Ivan BledDest Androsov, Maksim Neon Mescheryakov and me. Also, huge thanks to Mike MikeMirzayanov Mirzayanov for great systems Polygon and Codeforces.

Good luck to all the participants!

Our friends at Harbour.Space also have a message for you:

Hey, Codeforces!

We're excited to announce that registration for the Leagues of Code Summer Camp is now open! This year, Harbour.Space University and Leagues of Code are organising a programming camp in Menorca from July 1st to the 15th!

Our Summer Camp is a training program that will teach participants competitive programming. We are inviting students ages 10 to 18 interested in improving their skills or seeking intensive, high-level training. Participants will be divided into classes based on their level and previous experience. Classes will be held in English.

Join a coding camp that brings you the brightest stars in tech!

Here is a summary of the camp :

• Duration: 2 weeks
• Dates: July 1st to 15th
• Place: Menorca
• Levels:

1. Zero: Our "Zero" course is designed for anyone without programming experience. Through interactive lessons and engaging activities, they'll learn the fundamentals of coding and build a strong foundation for future learning

2. Beginner: Our beginner coding course is designed for participants who have some basic programming knowledge but want to take their skills to the next level. The course covers programming fundamentals and builds on prior knowledge, focusing on problem-solving, critical thinking, and project-based learning

3. Intermediate: Become a pro-grammarians by diving into the main concepts of web and game development. No coding experience? No problem! We'll help you get started, and by the end of the bootcamp, you'll be a coding ninja with a cool project under your belt!

4. Advanced: Ready to put your brain to the test? Our camp will have you solving algorithms like a pro and competing like a champion with the guidance of world medalists. By the end of camp, you'll be a coding champion with a trophy in your virtual hands!

Ready to join our Summer Camp in Menorca? We have a 30% discount for Codeforces participants using the code CODPARMEBO30.

UPD: Editorial is out

Hello Codeforces!

mesanu, flamestorm and I are very excited to invite you to Codeforces Round 859 (Div. 4)! It starts on Mar/19/2023 17:55 (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).

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 all testers: jampm, Max_Calincu, KrowSavcik, TimaDegt, nyaruhodo, tibinyte, badlad, Phantom_Performer, AlperenT, Bakry, keta_tsimakuridze, Gheal, RedstoneGamer22, Dominater069!

And thanks to Alexdat2000 for translating the statements!

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

Good Luck to everyone!

UPD: Editorial

Hi Codeforces!

Talaodi, YunQian, xukai and I mazihang2022 are excited to invite everyone to participate in Codeforces Round 858 (Div. 2), which will be held on Mar/18/2023 15:05 (Moscow time). Please note the unusual start time.

This round will be rated for participants with rating lower than 2100. We will be pleased to see the participants with a higher rating to take part in our round unofficially as well!

You will be given 6 problems to solve, one of which contains subtasks. You will have 2 hours and 15 minutes to solve them. Scoring distribution will be announced later.

We would like to thank everyone who helped with this round:

• errorgorn for coordinating the round. He really helped a lot as it's our first time setting up a round on Codeforces.
• Runtime-Terr0r, maomao90, mtw, milind0110, Dominater069, Codula, Everule, fengzhengwei, feecIe6418, AlperenT, 18o3 and rsj for testing the round and providing valuable feedbacks, and for all your help in improving this round's quality.
• Alexdat2000 for Russian translation.
• Talaodi for setting no problems finally being our mascot for the round.
• MikeMirzayanov for the great Codeforces and Polygon platforms.
• You, for participating in the round.

We are looking forward to your participation. Good luck and Have fun!

UPD1: Score distribution: $$$500-1000-1750-2000-2250-(2500+1500)$$$

UPD2: Editorial

UPD3: Congratulations to the winners!

Official winners:

1. MoFalkmusic
2. Goldenglowo
3. 2021_yes
4. Terry2022
5. gajar.nouka

Unofficial winners:

1. BucketPotato
2. MoFalkmusic
3. Goldenglowo
4. tute7627
5. 2021_yes