#include <iostream>
#include <string>
#include <algorithm>

using namespace std;

int main(){
    string s1, s2, p1, p2, x1, x2;
    cin >> s1 >> p1 >> x1;
    cin >> s2 >> p2 >> x2;
    if(p1 == p2){
        cout << -1 << endl;
    }else{
        if(p1.size() > p2.size() ||
            (p1.size() == p2.size() && p1 > p2)){
            cout << s1 << endl;
        }else{
            cout << s2 << endl;
        }
    }
    return 0;
}