#include <iostream>
#include <fstream>

using namespace std;

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

int n,nrp,d,nr,i;

int main()
{
    in>>n;

    for(i=2;i<=n;i++){
        for(d=2;d<=i/2;d++){
            if(i%d==0){
                nr=nr+1;
                break;
            }
        }
    }

    out<<nr-1;

    return 0;
}