#include <bits/stdc++.h>
using namespace std;
int main()
{
    string sa, sb, pa, pb, ans = "-1";
    char c;
    cin >> sa >> pa >> c >> sb >> pb >> c;
    int len = pa.length();
    if (pa.length() > pb.length()) ans = pa;
    else if (pa.length() == pb.length()) {
        while (len > 0) {
            if (pa[len-1] > pb[len-1]) {
                ans = sa;
                break;
            } else if (pa[len-1] < pb[len-1]) {
                ans = sb;
                break;
            }
            len--;
        }
    }
    else ans = pb;
    cout << ans << endl;
    return 0;
}