#include <iostream>
#include <fstream>

using namespace std;
ifstream in ("fractii.in");
ofstream out ("fractii.out");
int const nmax = 1000000;
int v[5 + nmax];

int main()
{
  int n;
  in>>n;
  long long s = 1;
  for(int j = 2 ; j <= n ;j++){
    v[j] += j - 1;
    for(int i = (j<<1) ;i <= n ;i += j){
      v[i] -= v[j];
    }
    s += (v[j]<<1);
  }
  out<<s;
  return 0;
}