/* -*- coding: utf-8 -*-
 *
 * 2552.cc:  No.2552 Not Coprime, Not Divisor - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 1000000;

/* typedef */

typedef long long ll;

/* global variables */

int phis[MAX_N + 1];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);

  for (int i = 1; i <= n; i++) phis[i] = i;

  for (int p = 2; p <= n; p++)
    if (phis[p] == p) {
      phis[p]--;
      for (int i = 2; i * p <= n; i++)
	phis[i * p] -= phis[i * p] / p;
    }
  
  ll sum = (ll)n * (n - 1) / 2;
  for (int x = 2; x <= n; x++)
    sum -= phis[x] + (n / x - 1);

  printf("%lld\n", sum);

  return 0;
}