def get_res(output: bytes) -> bytes:
    """Support function to get the 64-bit signed response (RES) from OUT2, the
    output of 3GPP f2 function.

    :param output: OUT2

    :returns: OUT2[64] .. OUT2[127]
    """
    lower_edge = 8  # = ceil(64/8)
    upper_edge = 16 # = ceil(127/8)
    return output[lower_edge:upper_edge]