#include <bits/stdc++.h>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

long long sum;
int n, phi[1000002];

void DaiCuPhi () {
  for (int i = 1; i <= n; i++)
    phi[i] = i;
  for (int i = 2; i <= n; i++)
    if (phi[i] == i) {
      for (int j = i; j <= n; j += i) {phi[j] /= i; phi[j] *= (i - 1);}
    }
}

int main()
{
  fin >> n;
  DaiCuPhi();
  for (int i = 1; i <= n; i++)
    sum += phi[i];
  fout << 2 * sum - 1;
  return 0;
}