#include <iostream>
#include <fstream>
using namespace std;
int main ()
{  unsigned int N, nrdiv=0, nrprime=0;
   ifstream fin("ciur.in");
   fin>>N;
   ofstream fout("ciur.out");
   for(unsigned int i=1;i<=N;i++){
    for(unsigned int j=1;j<=i;j++){
    if(i%j==0)nrdiv++;
    }
    if(nrdiv==2) nrprime++;    
   }
   fout<<nrprime;



    return 0;
}