#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cmath>
#include <string>
#include <vector>
#include <algorithm>
#include <queue>
#include <map>
#include <functional>
#include <set>
#include <numeric>
#include <stack>
#include <utility>
//#include "util.h"

using namespace std;
typedef long long lint;
typedef pair<lint, lint> Pii;

#define PI 3.14159265358979323846
#define EPS 1e-6
#define MOD ((lint)1000000007)
#define MIN(a,b) ((a)<(b)?(a):(b))
#define MAX(a,b) ((a)>(b)?(a):(b))



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