using System;
using System.Linq;
using System.Numerics;

class No201
{
    static void Main()
    {
        var f = Console.ReadLine().Split(' ');
        var s = Console.ReadLine().Split(' ');
        var fn = BigInteger.Parse(f[1]);
        var sn = BigInteger.Parse(s[1]);
        Console.WriteLine(fn - sn > 0 ? f[0] : fn == sn ?" -1" : s[0]);
    }
}