#include <bits/stdc++.h>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int n;

int Euler(int x){
  int rasp = 1;

  for(int d = 2; d*d<=x; ++d){
      if(x%d==0){
         rasp*=(d-1);
         x/=d;
         while(x%d==0){
            x/=d;
            rasp*=d;
         }
      }
  }

  if(x>1) rasp*=(x-1);

  return rasp;
}

int main(){

    ios_base::sync_with_stdio(false);

    f>>n;

    unsigned long long rasp = 1;

    for(int i = 2; i<=n; ++i) rasp+=2*Euler(i);

    g<<rasp;

    return 0;
}