#include <iostream>
#include <string>
using namespace std;

//文字列の要素はchar型なのでそのまま比較できる

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.length() > pb.length()) cout << sa << endl;
    else if(pa.length() < pb.length()) cout << sb << endl; 
    else cout << (pa > pb ? sa : sb) << endl;

    return 0;
}