#include<fstream.h>
int main ()
{
long n,i,j;
ifstream f("ciur.in");
ofstream g("ciur.out");
f>>n;
if(n>=2)
{long k=1;
 for(i=3;i<=n;i=i+2)
 {
  j=3;
  while(i%j!=0&&j<=i/2)j=j+2;
  if(j>i/2) k++;
 }
  g<<k;
}else g<<0;
f.close();
g.close();
return 0;
}