#include <iostream>
#include <fstream>
ifstream fin("ciur.in");
ofstream fout("ciur.out");
using namespace std;

int main()
{
    int n, prime = true, S = 0;
    fin >> n;
    for(int i = 2; i <= n; i++)
    {
        for(int j = 2; j < i; j++)
        {
            prime = true;
            if(i % j == 0)
            {
                prime = false;
                break;
            }
        }
        if(prime == true)
        {
            S++;
        }
    }
    fout << S << endl;
}