#include <bits/stdc++.h>
using namespace std ;
char b [ 2000001] ;
ifstream in ("ciur.in") ;
ofstream out ("ciur.out") ;
int sol = 1 , n , i , j ;
int main ()
{
    in >> n ;
    for ( i = 3 ; i <= n ; ++ i )
    {
        if ( !b[i] && i&1 )
        {sol ++ ;
        for ( j = i*3 ; j <= n ; j +=2*i )
        b [ j ] = 1 ;
        }
    }
    out << sol ;
}