#include <fstream>

using namespace std;

int eulerphi (int nr) {
  int prod = 1;
  int c = 2;
  bool flg;
  while (nr > 1) {
    flg = false;
    while (nr%c == 0){
      flg = true;
      prod *= c;
      nr /= c;
    }
    if (flg) { prod *= c - 1; prod /= c; }
    c++;
  }
  return prod;
}

int main(){
  int n, nr;
  ifstream fin("fractii.in");
  ofstream fout("fractii.out");
  fin >> n;
  
  nr = -1;
  for (int i = 1; i <= n; i++) nr += 2*eulerphi(i);
  
  fout << nr;
  fin.close();
  fout.close();
  return 0x0;
}