using System;

class Program
{
    static void Main()
    {
        string[] a = Console.ReadLine().Split();
        string[] b = Console.ReadLine().Split();

        string A = a[1];
        string B = b[1];

        if (A.Length > B.Length)
        {
            Console.WriteLine(a[0]);
            return;
        }
        else if (A.Length < B.Length)
        {
            Console.WriteLine(b[0]);
            return;
        }
        else
        {
            for (int i = 0; i < a[1].Length; i++)
            {
                if (A.CompareTo(B) > 0)
                {
                    Console.WriteLine(a[0]);
                    return;
                }
                else if (A.CompareTo(B) < 0)
                {
                    Console.WriteLine(b[0]);
                    return;
                }
            }
        }

        Console.WriteLine(-1);
    }
}