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

namespace YukiCoder
{
    class Program
    {
        static bool IsNum(string S)
        {
            if (S.Any(c => c < '0' || c > '9')) return false;
            if (S.Length == 1)                  return true;
            if (S[0] == '0')                    return false;
            return true;
        }

        static void Main(string[] args)
        {
            string a = Console.ReadLine();
            string b = Console.ReadLine();
            string S = (IsNum(a) && IsNum(b)) ? "OK" : "NG";
            Console.WriteLine(S);
            Console.ReadLine();
        }
    }
}