using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        string[] AB = new string[2];
        AB[0] = Console.ReadLine();
        AB[1] = Console.ReadLine();

        bool isOK = false;
        int chkNumeric = 0;

        foreach (string chkString in AB)
        {
            isOK = false;

            if (!int.TryParse(chkString, out chkNumeric)) { break; }
            if (1 < chkString.Length && chkString.Substring(0, 1) == "0") { break; }
            isOK = true;
        }
        Console.WriteLine(isOK ? "OK" : "NG");
    }
}