#include <bits/stdc++.h>

using namespace std;

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

#define N_MAX 1000001
int phi[N_MAX];

int main()
{
  int n, i, j;
  long long res;
  fin >> n;
  for(i = 1; i <= n; ++i) {
    phi[i] = i;
  }

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

  res = 0;
  for(i = 1; i <= n; ++i) {
      res += phi[i];
  }

  fout << res * 2 - 1 << '\n';

  return 0;
}