#include <cstdio>
#include <cmath>
using namespace std;
const int MAXN = 1000000;
int euler[MAXN + 5];
int main(){
  freopen("fractii.in", "r", stdin);
  freopen("fractii.out", "w", stdout);
  int n, i, j;
  long long s = 0;
  scanf("%d", &n);
  for (i = 1; i <= n; i ++)
    euler[i] = i;
  for (i = 2; i <= n; i ++)
    if (euler[i] == i)
      for (j = i; j <= n; j += i)
        euler[j] -= euler[j] / i;
    for (i = 1; i <= n; i ++)
      s += euler[i];
    printf("%lld\n", 2 * s - 1);
    return 0;
}