def main():
    Sa, Pa, Xa = map(str, input().split())
    Sb, Pb, Xb = map(str, input().split())

    if Pa == Pb:
        print(-1)
    elif len(Pa) > len(Pb):
        print(Sa)
    elif len(Pa) < len(Pb):
        print(Sb)
    else:
        if Pa > Pb:
            print(Sa)
        else:
            print(Sb)


if __name__ == "__main__":
    main()