I notice that sometimes the difficulty(a number from 800 to 3500) cannot reflect the true difficulty of a problem,
like: CF1603F
Only three strong programmers passed the problem: Two LGMs and rainboy, but its difficulty is only 2700.
I guess this low number may be because rainboy's rating (about 2000 at that time) is far below his real level.
So, I would like to know how codeforces determine the difficulty of the problems?
I think the problem is a modified version of 1174D - Ehab and the Expected XOR Problem which made it impossible for many LGMs to solve.
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