#include <bits/stdc++.h>
using namespace std;

string s1, s2;
string p1, p2, s;
void input() { cin >> p1 >> s1 >> s >> p2 >> s2 >> s; }
void solve() {
  string ans;
  if (s1 == s2) {
    ans = "-1";
  } else {
    if (s1.size() == s2.size()) {
      if (s1 > s2) {
        ans = p1;
      } else {
        ans = p2;
      }
    } else {
      if (s1.size() > s2.size()) {
        ans = p1;
      } else {
        ans = p2;
      }
    }
  }
  cout << ans << endl;
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  input();
  solve();
}