def get_mac_s(output: bytes) -> bytes:
    """Support function to get the 64-bit resynchronisation authentication code
    (MAC-S) from OUT1, the output of 3GPP f1* function.

    :param output: OUT1

    :returns: OUT1[64] .. OUT1[127]
    """
    edge = 8 # = ceil(63/8)
    return output[edge:]