package main

import . "fmt"
import . "math/big"

func main() {
	var s,t,u,v string
	a,b:=new(Int),new(Int)
	Scan(&s,a,&t,&u,b,&v)
	switch a.Cmp(b) {
		case 0:
		Println(-1)
		case 1:
		Println(s)
		case -1:
		Println(u)
	}
}