import java.util.Scanner;

public class No201 {

	public static void main(String[] args) {
		
		Scanner scanner = new Scanner(System.in);
		
		String[] spx1 = scanner.nextLine().split(" ");
		String[] spx2 = scanner.nextLine().split(" ");
		
		scanner.close();
		
		int n = spx1[1].compareTo(spx2[1]);
		
		if(n>0) {
			System.out.println(spx1[0]);
		}else if(n<0) {
			System.out.println(spx2[0]);
		}else {
			System.out.println(-1);
		}
	
	}

}