def get_monero_rct_type(bp_version=1):
    """
    Returns transaction RctType according to the BP version.
    Only HP9+ is supported, thus only Simple variant is concerned.
    """
    if bp_version == 1:
        return 3  # TxRctType.Bulletproof
    elif bp_version == 2:
        return 4  # TxRctType.Bulletproof2
    else:
        raise ValueError("Unsupported BP version")