using static System.Console;
class Simple {
    public static void Main(string[] args) { new Simple().Solve(); }
    string Sa, Pa, Xa;
    string Sb, Pb, Xb;
    int isAwin(string pa, string pb) {
        if (pa.Length != pb.Length) return pa.Length > pb.Length ? 1 : -1;
        for (var i = 0; i < pa.Length; ++i)
            if (pa[i] != pb[i]) return pa[i] > pb[i] ? 1 : -1;
        return 0;
    }
    void Solve() {
        var line1 = ReadLine().Split();
        var line2 = ReadLine().Split();
        Sa = line1[0];
        Pa = line1[1];
        Xa = line1[2];
        Sb = line2[0];
        Pb = line2[1];
        Xb = line2[2];
        var tmp = isAwin(Pa, Pb);
        var ans = tmp == 1 ? Sa : tmp == -1 ? Sb : "-1";
        WriteLine(ans);
    }
}