#include<iostream>
#include<stdio.h>
#include<map>

using namespace std;

int main(){

    string sa, pa, xa, sb, pb, xb;
    cin>> sa>> pa>> xa;
    cin>> sb>> pb>> xb;
    map<string, string> mp;
    mp[sa] = pa;
    mp[sb] = pb;

    if(mp[sa]==mp[sb]){
        cout<< -1<< endl;
        return 0;
    }

    if(mp[sa] < mp[sb]){
        cout<< sb<< endl;
    }else{
        cout<< sa<< endl;
    }
    return 0;
}