using System;

public class Hello
{
    public static void Main()
    {
        for (int i = 0; i < 2; i++)
        {
            var s = Console.ReadLine().Trim();
            if (!check(s)) { Console.WriteLine("NG"); goto end; }
        }
        Console.WriteLine("OK");
        end:;
    }
    public static bool check (string s)
    {
        for (int i = 0; i <= 12345; i++)
            if (i.ToString() == s) return true;
        return false;
    }
}