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 - Late For Work (submissions are not allowed). 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.