I just looked at the scoreboard of round 720 and was surprised by how a Div2 participant ([user:krasav4ik,2021-05-07]) 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 [submission:115581818], [submission:115571933]. I don't think they were written by the same person. Is this behavior considered as cheating?