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

ifstream f("ciur.in");
ofstream g("ciur.out");

int n;
const int NMAX = 2e6 + 5;
int v[NMAX], nr;

int main()
{
    f >> n;
    for(int i = 2; i <= n; i++) {
        bool ok = 1;
        for(int j = 1; j <= nr; j++) {
            if(i % v[j] == 0) {
                ok = 0;
                break;
            }
        }
        if(ok) {
            nr++;
            v[nr] = i;
        }
    }
    g << nr;
    return 0;
}