Hello Codeforces!
I am glad to invite you to Codeforces Round 1134 (Div. 4), which will take place on Nov/12/2026 17:35 (Moscow time). After quite a long break, I have taken up problem setting again — this time working together with AI agents. For me, this is an experiment in getting back into problem writing, and we will see together how successful AI turns out to be as a partner in this work. I am looking forward to seeing both Div. 4 participants competing officially and everyone else joining out of competition!
I am not sure that I will hit the exact difficulty expected of modern Div. 4 rounds, or satisfy all of your expectations and hopes, but it seemed to me that there is something beautiful in the problems I am offering. I urge you to resist the temptation to use AI to solve the problems or resort to any other form of cheating. Instead, let's go through this intellectual holiday together — me and all the honest participants — and make it a good, interesting competition. To avoid any confusion: I see AI as a tool, and it would be silly to turn down its help when developing Codeforces or preparing problems. But a tool should be used for the right things, and breaking the rules during a round is not one of them. During the contest, participants have rules to follow, and they apply to everyone.
I am very grateful to everyone who got involved, cared, and helped make this round happen:
- cry for coordinating the round. He was very attentive and tactful throughout the whole process. I was glad to work with him in exactly these roles — with me as the author and him as the coordinator — and I deeply appreciate his contribution to the community.
- Special thanks to Vladosiya for his many hours of work catching cheaters after every round. Unfortunately, I am sure that after this round, too, we will see big changes in the final standings as a result of his work.
- Our testers: AksLolCoding, aryanc403, Proof_by_QED, awoo, WorldWarV, Edeeva, lenarusw, yse, wakanda-forever, 2-qiym, simplelife, Vladosiya, 46657526buscaR, DivinePunishment, samsoom, chromate00, nik_exists, samyh, linearspace, youssef579, apollo07, vulestamenkovic, ayoooy, s83757, lattermatter, hannah12345, ethantran314 (and the list may still grow!).
Here are the format details for the round:
- 8 problems and 2 hours 15 minutes to solve them;
- 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 will be 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 unrated participants/newcomers).
Only trusted participants of the fourth division will be included in the official standings table. 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),
- have never had a rating of 1400 or higher.
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 (unless you choose to register unrated).
We urge participants whose rating is 1400+ not to register new accounts, but simply to take part unofficially. Please also remember the rule restricting AI use during the contest.
P.S. On a personal note, today is a truly special and meaningful milestone for me—my daughter just turned 15. I still remember sitting in the maternity ward 15 years ago with my laptop, deciding whether to postpone the round (spoiler: it did get postponed). How time flies... Happy birthday, my darling!
Good luck, and I hope you enjoy the problems!
