ID 1: See this coderorces ID ID1 This id was opened just before the contest.
ID 2: See this id also ID2
ID 3: See this id also ID3
ID2 and ID3 hacked 20 times of ID 1's solutions. All the submissions are similar. See the solutions Hacked submissions
I think it's cheating in codeforces. I think it will put a question towards codeforces. Hope codeforces authority will take proper steps for this cheating.