Problem:
Score : 100 points

Problem Statement

The door of Snuke's laboratory is locked with a security code.

The security code is a 4-digit number. We say the security code is hard to enter when it contains two consecutive digits that are the same.

You are given the current security code S. If S is hard to enter, print Bad; otherwise, print Good.

Constraints

S is a 4-character string consisting of digits.

Input

Input is given from Standard Input in the following format:

S

Output

If S is hard to enter, print Bad; otherwise, print Good.

Sample Input 1

3776

Sample Output 1

Bad

The second and third digits are the same, so 3776 is hard to enter.

Sample Input 2

8080

Sample Output 2

Good

There are no two consecutive digits that are the same, so 8080 is not hard to enter.

Sample Input 3

1333

Sample Output 3

Bad

Sample Input 4

0024

Sample Output 4

Bad

Solution in OCaml (4.02.3) (judge verdict: Accepted)

let inp : unit -> string = fun () -> 
  input_line stdin
let () =
  let s = inp () in
  let rec loop s n pred =
    if n = 0 then true
    else
      let a = s.[n - 1] in
      if a = pred then false
      else loop s (n - 1) a
  in
  if loop s 4 'a' then
    print_endline "Good"
  else
    print_endline "Bad"