#include <bits/stdc++.h>

using namespace std;

int main(void) {
  string s[2], p[2];
  char x[2];
  for (int i = 0; i < 2; i++) {
    cin >> s[i] >> p[i] >> x[i];
  }

  if (p[0].size() > p[1].size()) {
    cout << s[0] << endl;
  } else if (p[0].size() < p[1].size()) {
    cout << s[1] << endl;
  } else if (p[0] > p[1]) {
    cout << s[0] << endl;
  } else if (p[0] < p[1]) {
    cout << s[1] << endl;
  } else {
    cout << -1 << endl;
  }

  return 0;
}