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

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

        string pa = a[1];
        string pb = b[1];

        if (pa == pb)
        {
            Console.WriteLine(-1);
            return;
        }

        if (pa.Length > pb.Length)
        {
            Console.WriteLine(a[0]);
            return;
        }
        if(pa.Length < pb.Length)
        {
            Console.WriteLine(b[0]);
            return;
        }

        for (int i = 0; i < pa.Length; i++)
        {
            if (int.Parse(pa[i].ToString()) > int.Parse(pb[i].ToString()))
            {
                Console.WriteLine(a[0]);
                return;
            }

            if (int.Parse(pa[i].ToString()) < int.Parse(pb[i].ToString()))
            {
                Console.WriteLine(b[0]);
                return;
            }
        }

    }
}