var
 f:text;
 n,p,q,k:longint;
 phi:array[1..1000000] of longint;
 begin
  assign(f,'fractii.in');
  reset(f);
  readln(f,n);
  close(f);
  phi[1,1]:=1;
  for p:=2 to n do
   phi[p]:=p-1;
   for p:=2 to n do
     begin
      q:=2*p ;
      while q<=n do
       begin
        phi[q]:=phi[q]-phi[p];
        q:=q+p;
       end;
     end;
   k:=1;
  for p:=2 to n do
   k:=k+(2*phi[p]);

  assign(f,'fractii.out');
  rewrite(f);

   write(f,k);
   close(f);
   end.