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

using namespace std;
ifstream f("ciur.in");
ofstream g("ciur.out");
 int prim(long x)
 { int d,ok;
  if(x==0||x==1)
    return 0;
  else
     if(x%2==0)
       if(x==2)
         return 1;
       else
         return 0;
    else
    {
        d=3;   ok=0;
        while(d<=sqrt(x))
           if(x%d==0)
                   { x=d;
                    ok=1;
                    }
               else
               d=d+2;


     }
     if(ok==0)
        return 1;
     else
        return 0;

 }
int main()

{ long n,i,k;
  f>>n;
   k=0;
    for(i=1;i<=n;i+=2)
         if(prim(i))
            k++;
            g<<k;

}