Hi all,

I have difficulty on a problem on codeforces http://mirror.codeforces.com/problemset/problem/691/D

my submission is : http://mirror.codeforces.com/contest/691/submission/19308291

I think my idea is right, I used dsu to group several numbers and downsort numbers inside the groups. But I don't know why I am still wrong answer at test21. The idea is simple, but I can't find what's wrong. Anyone please help me, thanks:D

How to find bugs when you think your algorithms and implementation is correct,BTW?