Check if you're not using printf to output long long integers, it will not work on the server. So instead of:
printf("%lld\n", count);
do:
cout << count << endl;

I got WA on test 6 due to this problem.

I think for those who use C, %I64d is needed but not %lld, which only works on unix/linux. It's said that cout/cin in C++ is very very very slow when doing massive i/o work, especially for long long data.

the same code gives
WA on test#6 with G++ 4.7.2
AC on VC++

also AC with G++ 11