let chr_to_num c = Char.code c - Char.code '0'

let p s =
  let n = String.length s in
  let x = chr_to_num s.[0] in
  if n <> 1 && (x < 1 || x > 9) then false
  else
    let rec doit i =
      if i = n then true
      else
        let x = chr_to_num s.[i] in
        if x < 0 || x > 9 then false
        else doit (i + 1) in
    doit 1

let () =
  let a = read_line () in
  let b = read_line () in
  print_endline (if p a && p b then "OK" else "NG")