# -*- coding: utf-8 -*-
"""
No.201 yukicoderじゃんけん
https://yukicoder.me/problems/no/201

"""
import sys
from sys import stdin
input = stdin.readline


def solve(p1, p2):
    if len(p1[1]) > len(p2[1]):
        return p1[0]
    elif len(p1[1]) < len(p2[1]):
        return p2[0]
    if p1[1] > p2[1]:
        return p1[0]
    elif p1[1] < p2[1]:
        return p2[0]
    else:
        return '-1'


def main(args):
    p1 = input().split()
    p2 = input().split()

    ans = solve(p1, p2)
    print(ans)


if __name__ == '__main__':
    main(sys.argv[1:])