//
//  main.cpp
//  ciur lui erastostene
//
//  Created by Florian Marcu on 4/8/21.
//

#include <fstream>
#include <cmath>

using namespace std;

ifstream fin("ciur.in");
ofstream fout("ciur.out");
int c[2000000];
int main() {

    int n, i, j;
    fin >> n;

    c[0] = c[1] = 1;

    int k;
    for (i = 1; i <= sqrt(n); i++)
          if (c[i] == 0)
              for (j = 2; i*j <= n; j++)
                {
                    c[i*j] = 1;
                     k++;
                }

    fout << n-k<< "\n";




    return 0;
}