#include <iostream>

using namespace std;

int main(int argc, const char* argv[])
{
	string Sa, Sb;
	string Pa, Pb;
	string Xa, Xb;
	cin >> Sa >> Pa >> Xa;
	cin >> Sb >> Pb >> Xb;

	if (Pa == Pb) {
		cout << -1 << endl;
		return 0;
	}
	cout << (Pa.size() > Pb.size() || (Pa.size() == Pb.size() && Pa > Pb) ? Sa : Sb) << endl;
	return 0;
}