def safe_mathis_label(tput_true, tput_mathis):
    """
    Returns the Mathis model label based on the true throughput and
    Mathis model fair throughput. If either component value is -1
    (unknown), then the resulting label is -1 (unknown).
    """
    return (
        -1 if tput_true == -1 or tput_mathis == -1 else
        int(tput_true > tput_mathis))