I just looked at the scoreboard of round 720 and was surprised by how a Div2 participant (krasav4ik) was able to solve D in 13 minutes. Then I clicked on his submission for D and saw a very different style compared to his previous A, B, C submissions. Take a look at these submissions 115581818, 115571933. I don't think they were written by the same person. Is this behavior considered as cheating?

Update: oneninetyfive found this D submission is from StickBuerak. I don't know why but they keep downvoting my every comment probably in order to hide it so no one can see.