using System.Numerics;
using System;

public class Hello
{
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        var sa = line[0];
        BigInteger pa = BigInteger.Parse(line[1]);
        line = Console.ReadLine().Trim().Split(' ');
        var sb = line[0];
        BigInteger pb = BigInteger.Parse(line[1]);
        string ans;
        if (pa > pb) ans = sa;
        else if (pa < pb) ans = sb;
        else ans = "-1";
        Console.WriteLine(ans);
    }
}