#include<iostream>
#include<string>
#include<algorithm>
#include<vector>
#include<queue>
#include<map>
#include<math.h>
#include<iomanip>
#include<set>
#include<numeric>
#include<cstring>
#include<cstdio>
#include<functional>
#include<bitset>
#include<limits.h>
#include<cassert>
#include<iterator>
#include<complex>
#include<stack>
using namespace std;
#define lint long long int
/*
vector<char>al(26);
al = {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
vector<char>AL(26);
AL = {'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
*/

int main() {
	string SA, PA, XA, SB, PB, XB;
	cin >> SA >> PA >> XA >> SB >> PB >> XB;
	int sa = PA.size();
	int sb = PB.size();
	int cnt = 0;
	if (sa > sb) cout << SA << endl;
	else if (sa < sb) cout << SB << endl;
	else {
		for (int ia = 0; ia < sa; ia++) {
			if (PA.at(ia) > PB.at(ia)) {
				cout << SA << endl;
				cnt++;
				break;
			}
			else if (PA.at(ia) < PB.at(ia)) {
				cout << SB << endl;
				cnt++;
				break;
			}
		}
		if (cnt == 0) {
			cout << -1 << endl;
		}
	}
}