http://codeforces.net/contest/691/submission/20656594
http://codeforces.net/contest/691/submission/20656228
I wonder why one is AC but the other got TLE.
http://codeforces.net/contest/710/submission/20661365
http://codeforces.net/contest/710/submission/20661475
And one is AC but the other got CE.