package main

import (
	"fmt"
)

func main() {
	var sa, xa, sb, xb string
	var pa, pb []byte
	fmt.Scan(&sa,&pa,&xa)
	fmt.Scan(&sb,&pb,&xb)
	for i := range pa{
		if pa[i] > pb[i] {
			fmt.Println(sa)
			break
		} else if pa[i] < pb[i] {
			fmt.Println(sb)
			break
		} else if pa[i]==pb[i] && i == len(pa)-1 {
			fmt.Println("-1")
		}
	}
}