Hello, I am one of the participants of APIO 2025 (you can check at rank 44). The problems are really hard and tricky, and one of them is the 3rd problem — rotate. You guys can check the statements of APIO2025 in here: https://github.com/apio2025/apio2025_tasks.

I won't talk about the statement of the 3rd problem here since it's already in github; you guys should check that before reading my solution.

So, I don't know if this is the intended solution, but I think I am really lucky when I got accepted at 4h45. And that solution is really simple. Here's my solution:

I can't prove my solution, so can you guys check this and prove it for me, or is this solution wrong?

Thank you for reading this blog.

Today I checked standings in Codeforces Round 967 (Div.2). But I found some abnormal things.

This accout: https://codeforces.me/profile/ThMinh_, have a very good performance. But unusually, he got AC D in 31 mins, E1 in 2 mins later. So I was checked his submissions. And I found out that (may be) there are three people doing this contest in this account.

Why? Checking some submission's style code:

• https://codeforces.me/contest/2001/submission/277328121, https://codeforces.me/contest/2001/submission/277350871

• https://codeforces.me/contest/2001/submission/277358976, https://codeforces.me/contest/2001/submission/277368984

• https://codeforces.me/contest/2001/submission/277360719

So is this legit? And if not, please abort him.

Sorry if my English is bad.

At least, TrendBattles orz.