Scanf.scanf "%s %s" (fun a b ->
    let check s =
        let n = String.length s in
        let rec loop mode i =
            if i = n then true else
                if mode then (
                    if s.[i] >= '0' && s.[i] <= '9' then loop mode (i + 1) else false
                ) else (
                    if s.[i] >= '1' && s.[i] <= '9' then loop true (i + 1) else false
                )
        in
        if s = "0" then true else
            let f = loop false 0 in
            if f && int_of_string s <= 12345 then true else false
    in
    print_endline @@ if check a && check b then "OK" else "NG"
)