#include <fstream>

using namespace std;

int n, i, j, a[1000001];
long long sum = 1;

int main () {
  ifstream fi("fractii.in");
  ofstream fo("fractii.out");
  fi >> n;
  for (i = 2; i <= n; i++)
    a[i] = i-1;
  for (i = 2; i <= n; i++)
    for (j = i*2; j <= n; j += i)
      a[j] -= a[i];
  for (i = 2; i <= n; i++)
    sum += a[i]*2;
  fo << sum;
  return 0;
}