import sequtils, strutils

let
  a, b = stdin.readLine

var
  ans = "OK"

for x in [a, b]:
  if x.toSeq.anyIt(it in Letters):
    ans = "NG"
    break
  if x != "0" and x[0] == '0':
    ans = "NG"
    break
  let
    n = x.parseInt
  if n > 12345 or n < 0:
    ans = "NG"
    break

echo ans