func main()
	var _: [][]char
	do _ :: cui@input().split(" ")
	var Sa: []char :: _[0]
	var Pa: []char :: _[1]
	do _ :: cui@input().split(" ")
	var Sb: []char :: _[0]
	var Pb: []char :: _[1]
	
	var ans: []char :: "-1"
	if(Pa > Pb)
		do ans :: Sa
	elif(Pa < Pb)
		do ans :: Sb
	end if
	do cui@print("\{ans}\n")
end func