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

int main(){
    string s1,s2,s3;
    string t1,t2,t3;
    cin>>s1>>s2>>s3>>t1>>t2>>t3;
    if(s2==t2)cout<<-1<<endl;
    else if(s2.size()==t2.size())cout<<(s2>t2?s1:t1)<<endl;
    else cout<<(s2.size()>t2.size()?s1:t1)<<endl;
}