#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int,int>;
#define rep(i,n) for(int i=0;i<n;i++)

const ll mod = ll(1e9) + 7;
const int INF = 1<<29;

int main(){
    string sa,sb,pa,pb,xa,xb;
    cin >> sa >> pa >> xa >> sb >> pb >> xb;
    if (pa==pb) cout << -1 << endl;
    else if (pa>pb) cout << sa << endl;
    else cout << sb << endl;
    return 0;
}