#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef string str;
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    str s_a, p_a, x_a, s_b, p_b, x_b;
    cin >> s_a >> p_a >> x_a >> s_b >> p_b >> x_b;
    if (p_a == p_b) cout << "-1\n";
    else if (p_a.size() > p_b.size() || (p_a.size() == p_b.size() && p_a > p_b)) cout << s_a << "\n";
    else cout << s_b << "\n";
    return 0;
}