#include <fstream>
#include <cmath>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
long long a[2000100],n,z=0,j,i,nr=0,x;
int main()
{
    f>>n;
    for(i=2;i<=n;i++)
    {
        a[i]=1;
        j=2;
          while(j*j<=n)
          {
              while(z<=sqrt(n))
              {
            a[j*j+j*z]=0;
            z++;
              }
              z=0;
            j++;

          }
    }
    for(i=2;i<=n;i++)
        if(a[i]==1)
       nr++;
    g<<nr;

}