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

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