fnoihzhyan got rk1 on Codeforces Round 1000 (Div. 2). But his C-question code and F1 code have a sudden change in style. He uses <bits/stdc++.h> in question C and a lot of header files in question F1; Use 4 spaces for indentation in question C and tabs for indentation in F1; The #define at the beginning of the code is almost completely different. I think it's multiple people using the same account.
I'm not proficient in English, the above is machine translation.
his submissions are also very suspicious, solving F1 and D in two minutes, solving in a seemingly random way, and solving F2 in 11 minutes. its also most likely he is cheating because he suddenly went from doing really well at the start (which means he was most likely cheating), became pupil-specialist level in a few months, and now, in a few days, becomes around LGM level