#include <bits/stdc++.h>
using namespace std;

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);  
	
	string a, b, c, d, s, t;
	cin >> a >> s >> c;
	cin >> b >> t >> d;
	if(s.size() > t.size()) cout << a << endl;
	else if(s.size() < t.size()) cout << b << endl;
	else{
		if(s == t) cout << - 1 << endl;
		else if(s > t) cout << a << endl;
		else cout << b << endl;
	}
	return 0;	
}