#include <iostream>
#include <fstream>
using namespace std;

ifstream fin("ciur.in");
ofstream fout("ciur.out");
int main()
{
    int n, i, d, nrprime = 0;
    fin >> n;
    for (i = 2; i <= n; ++i) {
        bool prim;
        int nrdiv = 0;
        for (d = 1; d <= i; ++d) {
            if (i % d == 0)
                ++nrdiv;
        }
        if (nrdiv == 2)
            prim = true;
        else
            prim = false;

        if (prim)
            nrprime++;
    }
    fout << nrprime;
    return 0;
}