#include<fstream>
using namespace std;
long long a[1000100],n,s=1;
int i,j;
ifstream fin("fractii.in");
ofstream fout("fractii.out");

int main(){

  fin >> n;

  for (i=1; i<=n; i++)
   a[i]=i-1;
  for (i=2; i<=n; i++)
   for (j=i*2; j<=n; j=j+i)
    a[j]=a[j]-a[i];
  for (i=1; i<=n; i++)
   s=s+a[i]*2;

  fout << s;

 return 0;
}