#include <fstream>

using namespace std;

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

bool oneTime;
int n, i, j, prime;

int main()
{
    in >> n;
    prime = n;
    for(i = 2; i <= n; i++)
        if(i % 2 != 0
           || !oneTime)
           for(j = i * i; j <= n; j += i)
                prime--;
    out << --prime;
    return 0;
}