#include <fstream>
#include <bitset>
#define L 2000001
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
bitset <L + 1> c;
int main(){
  int n, i, d;
  for (i = 2; i * i <= L; i++)
    if (c[i] == 0)
      for (d = i * i; d <= L; d += i)
        c[d] = 1;
  fin >> n;
  d = 0;
  for (i = 2; i <= n; i++)
    d = d + 1 - c[i];
  fout << d << "\n";
  return 0;
}