import Data.Char

main = getContents >>= putStrLn . show' . all ok . words
 where show' p = if p then "OK" else "NG"

ok s
 | s == "0" = True
 | notElem (head s) ['1'..'9'] = False 
 | otherwise = let (n,xs) = head (reads s) in 0<=n && n<=12345 && null xs