#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef pair<int,int> P;
 
const int INF = 1e9;
const int mod = 1e9+7;
const double EPS = 1e-10;
const double PI = acos(-1.0);

int main()
{
    int ans = 0;
    string s1,s2,p1,p2,x1,x2;
    cin >> s1 >> p1 >> x1
        >> s2 >> p2 >> x2;
    if(p1.size() == p2.size()){
        for(int i = 0; i < p1.size(); i++){
            if(p1[i] == p2[i]) continue;
            if(p1[i] > p2[i]) ans = 1;
            else ans = 2; 
            break;
        }
    }else if(p1.size() > p2.size()) ans = 1;
    else ans = 2;
    if(ans) cout << (ans == 1 ? s1 : s2) << endl;
    else cout << -1 << endl;
    return 0;
}