program xuinea;
var a:array[0..9,1..1000000]of longint;
    n, i, j:longint; s:int64;
procedure calc;
var k:longint; p1:int64;
begin
  for i:=2 to n do
  if a[0,i]=0
  then begin
    j:=i;
    while j<=n do
    begin
      inc(a[0,j]);
      a[a[0,j],j]:=i;
      inc(j,i);
    end;
  end;
  s:=1;
  for i:=2 to n do
  begin
     p1:=i;
     for k:=1 to a[0,i] do
       p1:=p1*(a[k,i]-1)div a[k,i];
     s:=s+p1*2;
  end;
end;
begin
 assign(input, 'fractii.in');
 reset(input);
 read(n);
 close(input);
 calc;
 assign(output, 'fractii.out');
 rewrite(output);
 write(s);
 close(output);
end.