You may wonder: how is the guy who once said, “I have no problem doing a live verification,” and then deleted his blog doing now?

According to some of my friends, he qualified for the ECPC finals after solving 3 out of 4 problems in the qualifier (the first one was just a parity-checking problem). And then, in the ECPC finals, he solved only 1 out of 13 problems.

Despite that, he seems very proud of himself and keeps giving everyone advice. He is also trying to hide his identity by refusing to let the ECPC organizers take pictures of him, presumably because he would then be recognized as a Master who solved only the third problem during the frozen hour and failed to solve the fourth one.

He even told people on Codeforces to “wait and see” his performance in the ECPC. Well, now we have seen it.

Hope MikeMirzayanov takes a look at this soon.

I sincerely apologize for what happened when my friend used my computer and posted some random and inappropriate things on Codeforces. Those posts do not reflect my intentions or attitude, and I am sorry if they caused any annoyance or discomfort to anyone. I will be more careful about my account and make sure something like this does not happen again. I hope everyone can understand and forgive me.

Lately I've been trying to get into problemsetting, and one question keeps coming to mind: what actually makes a problem "great"?

I searched around a bit, and the only blog I found discussing this topic in depth was antontrygubO_o's "On problemsetting": https://codeforces.me/blog/entry/70178

The only problem is that it was written about 7 years ago. Since then, competitive programming has changed quite a lot, so I was wondering what people think nowadays.

I'd love to hear opinions from both experienced problemsetters and contestants.

Some questions I have:

• What makes a problem memorable or enjoyable to solve?
• What are the biggest mistakes beginner setters usually make?
• Are there any recent problems or contests that you think are great examples of good problemsetting?
• When creating problems, what do you care about the most? Originality? Elegance? Educational value? A nice story? Something else?
• How do you come up with new ideas without accidentally reinventing an existing problem?

Or just share your own thoughts about problemsetting in general. There probably isn't a single "correct" answer, so I'm interested in hearing different perspectives.

Hopefully this thread can become a nice collection of advice for people who want to write better problems.

Thanks!

Link to Manifold Market 1 Link to Manifold Market 2.

Will I finally reach Expert, or am I doomed to stay cyan forever? I made a prediction market about it. Feel free to check it out, and if you'd like, you can make a prediction with virtual mana (fake money). Sorry the previous one was resolved wrongly and I can't find the undo resolve button.

Edit: The market has now been unresolved, so everyone can make predictions again!

2nd edit: I sincerely apologize for the inconvenience. I've been overwhelmed with work this month, and I'm afraid I won't be able to meet the current deadline. Would it be possible to extend the time limit to September 1, 2026? I completely understand if that's not possible, and I really appreciate your understanding.

How can this code AC? Is this code illegal?

Today, I want to expose _Cinder, a user who recently reached the Master rank. After looking through his recent contests and submissions, I strongly believe that this account is cheating.

The account was an Expert with a rating of around 1600 in December 2025. After a break of about 1.5 years, the user suddenly returned and gained nearly 600 rating points within only three contests, reaching Master (2176). Such an improvement alone is not proof, but the submissions themselves are much more concerning.

The most recent contest was Order Capital Round 2, where the user solved seven problems. The coding style changes dramatically from one problem to another. In problems B, C, E, and G, the variable names are relatively short and simple. In problem D, underscores suddenly appear everywhere. In problem F, the code starts with one style and later switches to another style with many underscore-heavy variable names and additional helper functions. It looks as if two different people wrote different parts of the code.

The same thing happened in Educational Codeforces Round 191. Problems A through E1 use a fairly consistent template and coding style. However, the last submission for E2 is completely different. New helper functions suddenly appear, variable names become much longer, and the overall structure no longer resembles the earlier submissions. Such drastic changes within a single contest are highly suspicious.

The first contest after the user's return, Codeforces Round 1102, is even more concerning. The submissions contain extremely long variable names filled with underscores, a style that appears repeatedly in AI-generated code. Comparing these submissions with the user's previous coding style makes the difference very obvious.

Of course, any single piece of evidence may be explained away. However, when we combine the sudden 600-point rating increase, the six-month break, and the repeated changes in coding style both across and within contests, the conclusion becomes difficult to ignore.

In my opinion, this account is cheating. I hope the Codeforces administrators review these submissions carefully. If anyone disagrees, please explain why in the comments.

Note : underscore = '_'

Hope _Cinder won't use useless excuses anymore.