#include<iostream>
#include <math.h>
#include <string>
using namespace std;

int main(){
	string s1;
	string s2;
	string a1;
	string a2;
	string x1;
	string x2;
	int p1;
	int p2;
	cin >> s1;
	cin >> a1;
	cin >> x1;
	cin >> s2;
	cin >> a2;
	cin >> x2;
	p1 = a1.length();
	p2 = a2.length();
	if (p1 > p2){
		cout << s1 << endl;
	}
	else if (p1 < p2){
		cout << s2 << endl;
	}
	else{
		for (int i = 0; i < p1; i++){
			if (a1.substr(i, 1)>a2.substr(i, 1)){
				cout << s1 << endl;
				break;
			}
			else if (a1.substr(i, 1)<a2.substr(i, 1)){
				cout << s2 << endl;
				break;
			}
			else if (i == p1 - 1){
				cout << "-1" << endl;
			}
		}
		
	}
	return 0;
}