#include <fstream>
#include <bitset>

using namespace std;

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

int n, nr = 1;

bitset <2000005> p;

int main()
{
    cin >> n;

    p[1] = 1;

    for(int i = 2; i * i <= n; i++)
        if(p[i] == 0)
            for(int j = i * i; 1LL * j <= 1LL * n; j += i)
            {
                p[j] = 1;
                nr++;
            }

    cout << n - nr;

    return 0;
}