#include<bits/stdc++.h>
#define endl '\n'
#define MAXN 2000
using namespace std;

int main()
{
    string a, b;
    string c, d;
    char e, f;

    cin >> a >> c >> e;
    cin >> b >> d >> f;

    if(c > d)
        cout << a << endl;
    else
        if(c < d)
            cout << b << endl;
        else
            cout << -1 << endl;

    return 0;
}