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

int main() {
  string Sa, Pa, Xa;
  cin >> Sa >> Pa >> Xa;
  string Sb, Pb, Xb;
  cin >> Sb >> Pb >> Xb;
  if (Pa == Pb) {
    cout << -1 << endl;
  }
  else if (Pa.size() > Pb.size() || (Pa.size() == Pb.size() && Pa > Pb)) {
    cout << Sa << endl;
  }
  else {
    cout << Sb << endl;
  }
  return 0;
}