#include <fstream>
#define L 1000001
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int e[L + 1];
int main(){
  int n, i, j;
  long long s;
  fin >> n;
  for (i = 1; i <= L; i++)
    e[i] = i;
  for (i = 2; i <= L; i++)
    if (e[i] == i)
      for (j = i; j <= L; j += i)
        e[j] = e[j] / i * (i - 1);
  s = 0;
  for (i = 2; i <= n; i++)
    s = s + e[i];
  fout << s + s + 1 << "\n";
  return 0;
}