#include <bits/stdc++.h>
using namespace std;
int main(){
string sa,pa,xa,sb,pb,xb;
cin>>sa>>pa>>xa>>sb>>pb>>xb;
if(pa.length() != pb.length()) {
cout << (pa.length() < pb.length() ? sb : sa) << endl;
} else if (pa != pb) {
cout << (pa < pb ? sb : sa) << endl;
} else {cout << -1 << endl;}
}