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

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

int n;
vector<int> v;

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