import sys


def main():
    sys.setrecursionlimit(100000)
    SA, PA, XA = input().split()
    SB, PB, XB = input().split()

    n = max(len(PA), len(PB))
    pa, pb = PA.zfill(n), PB.zfill(n)
    for ai, bi in zip(pa, pb):
        if ai < bi:
            ans = SB
            break
        elif ai > bi:
            ans = SA
            break
    else:
        print(-1)
        return
    print(ans)


if not __debug__:
    f = open(sys.argv[1], "r")
    sys.stdin = f

main()