#include <fstream>
#include <bitset>

using namespace std;

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

bitset <10000000> prim;

int main()
{
    int n, sol=1,max=10000000;

    f>>n;
    prim[2]=1;
    for (int i=3; i<=n; i+=2) prim[i] = 1;
    for (int i=3; i<=n; i+=2)
      if (prim[i])
      {
          ++sol;
          for (int j=i+i; j<=n; j+=i) prim[j]=0;
      }
    g<<sol<<'\n';
    f.close(); g.close();
    return 0;
}