#include<fstream.h>
#include<math.h>

long n,a,d,b,nr;
char v[2000001],gasit;

int main()
{
 ifstream f("ciur.in");
 ofstream g("ciur.out");
 f>>n;
 b=sqrt(n);
 nr=1;
 d=3;
 while(d<=b)
  {
   a=d;
   while(a<=n){v[a]=1;nr++;a+=d;}
   gasit=0;a=d+2;
   while(!gasit)
   {
    if(!v[a]){d=a;gasit=1;}
    else a+=2;
    }
   }
 g<<nr;
 return 0;
 }