http://codeforces.com/gym/101194
只有2^3 - 1可以
#include <bits/stdc++.h>
using namespace std;
int main()
{
int T;
scanf("%d", &T);
for (int i = 1; i <= T; i++) {
int N;
scanf("%d", &N);
printf("Case #%d: %d\n", i, N / 3);
}
}