#include <iostream>
#include <string>
using namespace std;
int main() {
	string Sa, Sb;
	string Pa, Pb;
	char Xa, Xb;
	cin >> Sa >> Pa >> Xa;
	cin >> Sb >> Pb >> Xb;

	if (Pa > Pb) {
		cout << Sa << endl;
	}
	else if(Pa == Pb){
		cout << -1 << endl;
	}
	else {
		cout << Sb << endl;
	}
	return 0;
}