#include <fstream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.in");
int main()
{

    int n,i,j,nr,p[10001];
     nr=1;
     fin>>n;
    for (i = 3; i <= n; i += 2) {
      if (p[i] == 0) {
        nr++;
        for (j = i + i + i; j <= n; j += i << 1) {
          p[j] = 1;
        }
      }
    }
    fout<<nr;
    return 0;
  }