#include <iostream>
#include <string>
using namespace std;
int main(){
	string SA, PA;
	char XA;
	cin >> SA >> PA >> XA;
	string SB, PB;
	char XB;
	cin >> SB >> PB >> XB;
	if (PA == PB){
		cout << -1 << endl;
	}
	if (PA.size() > PB.size() || PA.size() == PB.size() && PA > PB){
		cout << SA << endl;
	}
	if (PA.size() < PB.size() || PA.size() == PB.size() && PA < PB){
		cout << SB << endl;
	}
}