#include <iostream>
#include <fstream>

using namespace std;

int prim(int a)
{
  int i,k=0;

  for (i=1;i<=a;++i)
    if (a%i==0)
      k++;
  if (k==2)
    return 1;
  else return 0;

}

int main()
{
  int n,i,k=0;

  ifstream f("ciur.in");
  ofstream g("ciur.out");

  f>>n;

  for (i=1;i<=n;++i)
    if (prim(i)==1)
      k++;
  g<<k;

  return 0;
}