It's a really unfair and sad gesture by Igor_Parfenov, author of latest Div2_992 round, Problem C was exact copy of problem : https://codeforces.net/contest/513/problem/B2

This is extremely unfair to the people who tried this problem for the first time. This also explains why so many people were able to do this problem despite it being good enough, that most of the experts in my friend-list couldn't do it.

My submission for contest problem 992C : 295640125

Exact same code submission for older version 592B2 : 295644907

Edit: I don't want to put allegations on the author of the contest, as it could be a highly improbable coincidence that he thought the exact some problem. This blog is just to highlight the fact that fairness of the contest was compromised.