#include <iostream>
#include <string>

int scmp(const std::string& s, const std::string& t) {
    if (s.length() != t.length()) {
        return s.length() > t.length() ? 1 : -1;
    } else {
        return s == t ? 0 : s > t ? 1 : -1;
    }
}

void solve() {
    std::string sa, pa, sb, pb;
    char tmp;
    std::cin >> sa >> pa >> tmp >> sb >> pb >> tmp;

    int pres = scmp(pa, pb);

    std::cout << (pres == 0 ? "-1" : pres > 0 ? sa : sb) << std::endl;
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}