#include<fstream>

using namespace std;

ifstream in ("ciur.in");
ofstream out ("ciur.out");

bool v[200000];
int main ()
{
    int n,x=0,i,j;
    in>>n;
    for (i=2;i<=n;i++)
      for (j=2;j<=i/2;j++)
      {
        if (i%j==0)
        {
            v[i]=1;
            break;
        }
        else v[i]=0;
      }
      for (i=2;i<=n;i++) if (v[i]==0) x++;
    out<<x;
    in.close();
    out.close();
    return 0;
}