#include <bits/stdc++.h>
using namespace std;
int main (){
    vector<string> N(2);
    string R1,R2,P1,P2;
    cin >> N[0] >> R1 >> P2 >> N[1] >> R2 >> P2;
    cout << (R1==R2 ? "-1" : N[!(R1.size()>R2.size()||(R1.size()==R2.size()&&R1>R2))]) << endl;
    return 0;
}