#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 > pb) cout << sa << endl;
    else cout << sb << endl; 

    return 0;
}