import java.util.Scanner;
import java.util.stream.IntStream;

public class Main{
	static IntStream REPS(int v){return IntStream.range(0,v);}
	static IntStream REPS(int l,int r){return IntStream.rangeClosed(l,r);}
	static IntStream INS(int n) {return REPS(n).map(i->getInt());}
	static Scanner s=new Scanner(System.in);
	static int getInt(){return Integer.parseInt(s.next());}

	public static void main(String[]$){
		String na=s.next();
		String a=s.next();
		s.next();
		String nb=s.next();
		String b=s.next();
		
		if(a.equals(b)) {
			System.out.println(-1);
			return;
		}
		if(a.length()>b.length()) {
			System.out.println(na);
			return;
		}
		if(a.length()<b.length()) {
			System.out.println(nb);
			return;
		}
		if(a.compareTo(b)>0){
			System.out.println(na);
			return;
		}
		System.out.println(nb);
	}
}