#include <iostream>
#include <cstdio>

using namespace std;

int main()
{
    freopen("ciur.in", "r", stdin);
    freopen("ciur.out", "w", stdout);
    int n, a = 0, ok = 0;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++)
    {
        ok = 1;
        for(int j = 2; j < n/2; j++)
        {
            if(i % j == 0)
            {
                ok = 0;
            }
            if(ok == 1)
            {
                a++;
                break;
            }
        }
    }
    printf("%d", a - 1);

}