#include <bits/stdc++.h>

using namespace std;

int main()
{
  string S, T;
  string A, C;
  char B, D;

  cin >> S >> A >> B;
  cin >> T >> C >> D;

  if(A.size() > C.size() || (A.size() == C.size() && A > C)) {
    cout << S << endl;
  } else if(A == C) {
    cout << -1  << endl;
  } else {
    cout << T << endl;
  }
}