#include <fstream>
#include <iostream>
#include <cmath>
#include <bitset>
using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
bitset <2000000> a;
char b[2000000];
int u,i,j,nr;
int main()
{
     f>>u;
     nr=u;
    for (i=2;i*i<=u;i++)
        for (j=i*i;j<=u;j+=i)
             {
                 a[j]=1;
                 nr--;
             }


      g<<nr-1;
   f.close();
   g.close();
}