#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int main()
{ int n,i,j,a[1000001];
  long long cont=1;
  fin>>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[j] - a[i];
  for (i = 2; i <= n; i++)
    cont = cont + a[i]*2;
  fout << cont;
  return 0;
}