#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
using namespace std;
vector<pair<string,string> > v;
bool cmp(pair<string, string> a, pair<string, string> b){
    if (a.first == b.first){
        puts("-1");
        exit(0);
    }
  /*  if (a.first.size() != b.first.size()){
        if (a.first.size() > b.first.size()){
            cout << a.second << endl;
        }
        else{
            cout<<b.second << endl;
        }
        exit(0);
    }*/
    if (a.first < b.first){
        cout << b.second << endl;
    }
    else{
        cout << a.second << endl;
    }
    exit(0);
}
int main(){
    for (int i = 0; i < 2; i++){
        string a;
        string b;
        char c;
        cin >> a >> b >> c;
        v.push_back(make_pair(b, a));
    }
    sort(v.begin(), v.end(),cmp);
    return 0;
}