Qualification Round starts today at 17:35 MSK!

Good day, dear Codeforces users!

We would like to remind you that in less than 8 hours (at 17:35 Moscow time, UTC+3), the Qualification Stage of our contest series based on Sirius Educational Centre problems will begin!

Detailed rules, the scoring system, and track distribution criteria can be found in our main announcement.

Key Details of the Qualification Round:

• Format: You will be given 7 problems.
• Duration: Exactly 3 hours (until 20:35 MSK).
• Registration Link: Register for the Qualification Stage

Important Rating Restrictions for Prizes:

• Absolute Maximum: Users with a maximum rating above 1900 are not eligible for prizes at all.
• Advanced Track (DSA-Advanced): ALL participants with a maximum rating of 1900 or lower can compete for prizes (provided they successfully pass the qualification).
• Basic Track (DSA-Basic): Only participants with a maximum rating of 1600 or lower are eligible to compete for prizes here.

Fair Play and Feedback

• Anti-cheat: We kindly request everyone to follow the fair play rules. In case of any suspicion of plagiarism or AI usage, a participant will receive a warning and may be disqualified, with their results cancelled.
• Results: Passing scores for the second stage will be published no later than 10.10.2026.
• Questions during the contest: During the round, the jury will try to answer all incoming questions as quickly as possible (usually taking no more than 20 minutes).

Acknowledgments

I would like to express my deepest gratitude to my friend and tester — zeyd1234. Without him and his help, none of this would have been possible!

Thank you all, and see you at the round! Good luck!

[Prizes RF Only / Statements EN & RU] Prizes from Sirius Educational Centre: IOI-format Contest!

⚠️ NOTICE FOR INTERNATIONAL USERS

Good news: All problem statements will be fully available in both English and Russian! You are more than welcome to participate and solve the problems. Please note that physical prize delivery is strictly limited to the Russian Federation via Ozon, but everyone can compete for fun and practice!

Good day, dear Codeforces users!

We are glad to present you a contest that is fully identical to the selection process for the computer science educational program at the Sirius Educational Centre. Over the course of three weeks, exciting problem sets await you. The top participants will receive prizes personally from me and the Sirius Educational Centre!

IMPORTANT: Participation Restriction

We kindly request those who have already participated in the official selection for the "Informatics. Regions" program at Sirius: please do not participate in this contest. The problems will be completely identical!

Schedule and Registration Links

• Round 1 (General Selection):
• Date and Time: 03.10.2026 at 17:35 (Moscow time, UTC+3).
• Duration: 3 hours.
• Who can participate: Everyone is welcome!
• Registration Link: Qualification Stage
• Results publication: No later than 10.10.2026.

• Round 2 (Finals by Tracks):

• Date and Time: 18.10.2026 at 17:35 (Moscow time, UTC+3).
• Duration: 1 hour.
• Who can participate: Everyone is welcome (however, only those who passed Round 1 are eligible for prizes).
• Registration Links:
  • Final Stage (DSA-Basic)
  • Final Stage (DSA-Advanced)
• Final results publication: No later than 23.10.2026.

Round 1 Rules and Scoring System

• Format: You will be given 7 problems, with a maximum score of 100 points for each.
• Testing System: The contest uses IOI rules. Each problem contains subtasks with a fixed number of points (details can be found in the problem notes).
• Grading details: WA, TLE, MLE, or any other verdicts on individual tests do not stop the grading process — your solution will be tested on all test cases in the set.
• Standings ranking: Participants are sorted by the number of problems solved with a score of 80+ points. In case of a tie, the total number of points is used.
• Advancement criterion: At least 30% of all participants are guaranteed to advance to the second stage. Passing scores and lists will be published no later than 10.10.2026.

Round 2: Tracks and Distribution

The final round is split into two parallel competitions: 1. DSA-Basic (Algorithms and Data Structures: basic level). 2. DSA-Advanced (Algorithms and Data Structures: advanced level).

Please note: In the second round, the problems on both tracks will also be evaluated using the IOI system with a maximum score of 100 points per problem.

Access to solving problems will be open to all users, but only those who successfully passed Round 1 can compete for prizes. Based on the results of the first stage, you may be assigned one of three statuses:

1. Choice — you scored a high mark and can officially participate in either of the two tracks in Round 2 with a chance to win a prize.
2. DSA-Basic — you passed the selection, but you can only claim prizes if you participate in the basic track.
3. DSA-Advanced — a mandatory status for participants who have ever had a rating of 1600+ and scored enough points to pass. You can only participate in the advanced track.

Based on the results of Round 2, the Top-1 among official participants in each track will receive prizes!

Prize Delivery Information

• Prizes are shipped exclusively via the Ozon delivery service and only within the Russian Federation (no shipping outside the RF).
• If you win a prize, you need to contact me personally and provide the address of the specific Ozon pickup point (PVZ) where the package should be sent.
• If there is no Ozon pickup point in your city, but you live within the RF, the delivery will be handled individually — in this case, you must also contact me to arrange it.

Important Restrictions and Fair Play Rules

• Rating restrictions: We do not recommend participating for users with a rating above 1800. Users with a rating above 1900 are not eligible for prizes.
• Anti-cheat: A strict fair play policy applies to this contest. The use of AI (ChatGPT, etc.), assistance from third parties, and plagiarism are strictly prohibited. Violators will be disqualified, and their accounts will be banned.

Acknowledgments

We express our deepest gratitude to the Sirius Educational Centre for providing the educational materials and problems! Special thanks to my friend and tester — zeyd1234.

If you have any questions regarding the rules, scoring system, or advancement criteria, feel free to ask them in the comments below, and I will surely reply!

Good luck to everyone!

Hello Codeforces!I have prepared a complete, beginner-friendly problem set designed specifically for a Div. 4 round.Crucially, the entire package is already finished in Polygon — all tasks have validators, generators, and initial test sets ready. I am fairly confident that most of the problems will pass review without any issues.However, I don't know whom to officially send this Div. 4 set to, and due to a very tight personal schedule, I will not have the time to make technical revisions or handle potential test failures during the review process. Furthermore, I currently don't have a co-author who could come up with and add backup problems in case a task gets rejected due to an accidental duplicate (overlapping ideas with past contests).Because of this, I am looking for a co-author / partner to take over the project.What is already done:100% complete problem concepts, statements, and balancing for Div. 4.Fully working Polygon packages (generators, validators, checkers, main solutions).What is expected from a co-author:Handle any required fixes, edge-case testing, or minor rewrites in Polygon if the testing team requests changes.Bring or come up with a few backup problems to safeguard the round in case of any issues.Since the heavy lifting of writing Polygon scripts from scratch is completely done, this should be a very straightforward and smooth process for someone who has the time to manage the technical feedback loop.Please PM me directly here on Codeforces if you are interested in co-authoring this round!

Dear Codeforces users! My life is starting to feel a bit like a Black Mirror episode. I've realized my contribution is already low anyway due to toxic downvoting under every post. So I’m going to do what many want to do but are too afraid of losing their contribution to actually say. To everyone who downvotes posts for no reason: Shame on you. I genuinely despise this behavior, as it makes the community system completely unfair.I'm keeping this post civil only because younger users might read it, but my real feelings are much stronger. Feel free to downvote this post to oblivion, I honestly do not care anymore. I will continue to solve problems, and your groundless negativity won't stop me — it only shows I'm moving in the right direction.I deeply respect those who judge content objectively, and I strongly dislike those who just downvote everything blindly. I already know that I can write decent code, so I'll survive this. But if I were a newbie trying to share a self-made contest, this toxic feedback would make me quit the platform forever. Think about that. That is all. Thanks for reading. I know this post will tank my contribution to the very bottom, but I've already come to terms with it.

Hello Codeforces! I am glad to present to you a new mashup composed of problems from various April Fools Day contests!I have selected what I consider to be the best and most solvable problems and gathered them into a single contest. I did my best to pick tasks that can either be solved straight away or require just a little bit of brute force — you won't see problems like this one which require massive brute force. Please do not look up or steal solutions from others, solve them on your own! There will be 10 problems in total and a 48-hour window to solve them. The problem indexing also features some April Fools elements, so you could say the problems are not sorted by difficulty. The contest starts on September 12 at 21:00 (UTC+3), right after Codeforces Round 1120 (Div. 1, Div. 2) finishes (well, almost right after, since the author is human too and needs a small break). Good luck and high ratings to everyone in the upcoming official round, and have fun! You can join the contest using this link: https://codeforces.me/contestInvitation/8c00638c42c658c09b39f436f3c7ca1013cadcad Or you can join the group where the contest is hosted and where similar events will be posted in the future: https://codeforces.me/group/uTeivTi6Ym Thank you for your attention, and I hope to see you in the standings!