#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int main()
{
    int n;
    fin >> n;
    int i = 2;
    int suma = 0;
    while (i <= n)
    {
        int d = 2;
        int nr = 0;
        while(d <= i / 2)
        {
            if (i % d == 0)
            {
                nr++;
            }
            d++;
        }
        if (nr == 0)
        {
            suma++;
        }
        i++;
    }
    fout << suma;
}