#coding=UTF-8
#my 1st python code using dvorak

name=list(range(0,2,1))
yuru=list(range(0,2,1))

mojir=input()
hyo=mojir.split(" ")

name[0]=hyo[0]
yuru[0]=hyo[1]

mojir=input()
hyo=mojir.split(" ")

name[1]=hyo[0]
yuru[1]=hyo[1]

if yuru[0]>yuru[1]:
    print(name[0])
elif yuru[0]<yuru[1]:
    print(name[1])
else:
    print("-1")