using System;

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

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

                if (A.CompareTo(B) > 0) 
                {
                    Console.WriteLine(a[0]);
                    return;
                }
                else if(A.CompareTo(B) < 0)
                {
                    Console.WriteLine(b[0]);
                    return;
                }
            }
        }

        Console.WriteLine(-1);
    }
}