#include <bits/stdc++.h>

using namespace std;
typedef long long ll;

#define rep(i, n) for (int i = 0; i < (int)(n); i++)

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