#include <bits/stdc++.h>
using namespace std;

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

int n, cont;
char f[2000005];

int main()
{

    in>>n;

    for( int i = 1; i <= n; i++ )
        f[i] = '0';

    for( int i = 2; i <= n; i++ )
        for( int j = i; j*i <= n; j++ )
            f[i*j]++;

    for( int i = 2; i <= n; i++ )
        if( f[i] == '0' )
            cont++;

    out<<cont;

    return 0;
}