#include <bits/stdc++.h>
using namespace std;
ifstream fin ("ciur.in");
ofstream fout ("ciur.out");
const int Nmax =  2000005;
bitset < Nmax > a;
int n;
int main()
{
    fin >> n;
    a[1] = 1;
    for(int i = 2 ; i <= n ; i++)
        if(a[i] == 0)
            for(int j = 2 * i ; j <= n ; j += i)
                a[j] = 1;
    fout << n - a . count() << "\n";
    fin.close();
    fout.close();
    return 0;
}