#include <cstdio>
using namespace std;
int n,i,nr,j;
char p[2000010/2/8+1];
int main()
{
    freopen("ciur.in","r",stdin);
    freopen("ciur.out","w",stdout);
    scanf("%d",&n);
    nr=1;
    for (i = 1; ((i * i) << 1) + (i << 1) <= n; i += 1) {
    if ((p[i >> 3] & (1 << (i & 7))) == 0) {
      for (j = ((i * i) << 1) + (i << 1); (j << 1) + 1 <= n; j += (i << 1) + 1) {
        p[j >> 3] |= (1 << (j & 7));
      }
    }
  }
  for (i = 1; 2 * i + 1 <= n; i++)
       if ((p[i >> 3] & (1 << (i & 7))) == 0)
           nr++;
    printf("%d",nr);
    return 0;
}