using System;
using System.IO;
using System.Linq;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Numerics;
using System.Threading.Tasks;
using System.Text.RegularExpressions;
using static System.Math;
using Debug = System.Diagnostics.Debug;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;


static class P
{
    static void Main()
    {
        var a = Console.ReadLine().Split();
        var b = Console.ReadLine().Split();
        var pa = int.Parse(a[1]);
        var pb = int.Parse(b[1]);
        Console.WriteLine(pa > pb ? a[0] : pa < pb ? a[1] : "-1");
    }
}