Comment by gus_massa

I evaluated a lot of Math Olympiads in Argentina. Humans participants many times don't have a clear sense of whether they solved a problem correctly. We get review request of the grades, sometimes it's a mistake but the grader, sometimes it's a tricky error that changes the result very little, sometimes the human participant made a chain of huge mistakes that make no sense. (Obviously, we give a polite reply in every case.)