program fractii;

var
  n, i,j, z,x,k,m: longint;
  in_f, out_f: text;
  num:real;
  phi: array[1..1000000] of real;
  ok: boolean;

begin
  assign(in_f, 'fractii.in');
  assign(out_f, 'fractii.out');
  reset(in_f);

  readln(in_f, n);

for i:=1 to n do
 phi[i]:=i;

for i:=2 to n do
   if (phi[i]=i) then
   begin
     j:=i;

   while j<=n do
     begin

     phi[j] := phi[j]/i;
     phi[j] := phi[j]*(i-1);
       j:=j+i;
      end;
      end;
for i := 1 to n do num:=num+phi[i];
num:=num*2-1;





  rewrite(out_f);
  write(out_f, round(num));
  close(out_f);

end.