#include<iostream>
#include<cmath>
#include<vector>
#include<string>
#include<set>
#include<iomanip>
using namespace std;
int main() {
    string Sa, Pa, Xa, Sb, Pb, Xb; cin >> Sa >> Pa >> Xa >> Sb >> Pb >> Xb;
    if(Pa == Pb){
        cout << -1 << endl;
    }else if(Pa.size() > Pb.size()){
        cout << Sa << endl;
    }else if(Pa.size() < Pb.size()){
        cout << Sb << endl;
    }else if(Pa.size() == Pb.size()){
        for(int i = 0; i < Pa.size(); i++){
            if(Pa[i] - '0' > Pb[i] - '0'){
                cout << Sa << endl;
                break;
            }else if(Pa[i] - '0' > Pb[i] - '0'){
                cout << Sb << endl;
                break;
            }
        }
    }
    return 0;
}