#include <iostream>
#include <fstream>

using namespace std;
ifstream in ("ciur.in");
ofstream out ("ciur.out");

bool prim (int a)
{
    int b=0;
    if (a>1)
    {

        for (b=2; b<a-1; b++)
        {
            if (a%b==0)
            {
                return 0;
            }
        }
        return 1;

    }
    return 0;
}



int main()
{
    int n,i, rez=0;

    in>>n;

    for (i=1; i<=n; i++)
    {
        if (prim (i)==1)
        {
            rez++;
        }
    }

    out<<rez;





    return 0;
}