#include <bits/stdc++.h>   using namespace std;   int q[3001], t, n;   int main() {     scanf( %d , &n);     for (int i = 2; i <= n; i++) {       if (q[i - 1] == 2) t++;       if (q[i] > 0) continue;       for (int j = i; j <= n; j += i) q[j]++;     }     if (q[n] == 2) t++;     printf( %d n , t);   }   