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

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            string s1 = Console.ReadLine();
            string s2 = Console.ReadLine();
            bool flag = !((s1[0] == '0' && s1.Length != 1) || (s2[0] == '0' && s2.Length != 1));
            for (int i = 0; i < s1.Length; i++)
            {
                if (s1[i] < '0' || '9' < s1[i]) flag = false;
            }
            for (int i = 0; i < s2.Length; i++)
            {
                if (s2[i] < '0' || '9' < s2[i]) flag = false;
            }
            Console.WriteLine(flag ? "OK" : "NG");
        }
    }
}