#include <iostream>
#include <fstream>
using namespace std;
int a[100];
int main()

{
    int i, n, t, b, c=0;
    ifstream fin("ciur.in");
    ofstream fout("ciur.out");
    fin>>n;
    for (i=2; i<=n; i++){ t=i;
                        while (t<=n) {
                                    b=i*t;
                                    a[b]=1;
                                    t++;
                                    }
                        }

    for (i=2; i<=n; i++)
                        {
                         if (a[i] == 0) c++;
                        }
    fout<<c;



    return 0;
}