While solving random problems on DMOJ I found this problem: Problem, Contest the problem appeared in. I only read the statement and decided it was not for me, so I moved on. Today after the round I remembered this problem because it seemed similar to 1726F - Опоздать на работу (отправка решений запрещена). Not only are the problems exactly the same, they even share the same sample and the explanation of the sample is also the same:

Together with the fact that little_angel has solved this problem on DMOJ:

I am convinced that the authors of Codeforces Round 819 (Div. 1 + Div. 2) and Grimoire of Code Annual Contest 2022 have purposefully copied the problem and didn't even try to hide it. I don't think the contest should be unrated, because the impact was not that big. But I still believe that this is unacceptable for Codeforces contests. You are supposed to create original problems.