#include <iostream>
#include <string>
using namespace std;

int main()
{
    string sa,sb,pa,pb,xa,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{
        for(int i = 0; i < pa.length(); i++){
            if(pa[i] > pb[i]){
                cout << sa << endl;
                break;
            }if(pa[i] < pb[i]){
                cout << sb << endl;
                break;
            }
        }
    }
    return 0;
}