#include <iostream>
#include <fstream>

using namespace std;

int main()
{
    ifstream fin ("ciur.in");
    ofstream fout ("ciur.out");

    int n, contor=0;
    int prim = 0 ;
    int i, j ;
    fin>>n;
    for(i = 2; i<=n; ++i)
    {
        prim = 0 ;
        for ( j=2; j<=i - 1 ; ++j)
            if (i % j == 0)
                ++ prim ;
        if(prim == 0)
            ++ contor ;
    }
    fout << contor << '\n';
    fin.close();
    fout.close();

    return 0;
}