def get_si(simpos):
    """
    Get SI corresponding to the given SIM position.
    """
    if ((simpos >= 82109) and (simpos <= 104839)):
        si = 'ACIS-I'
    elif ((simpos >= 70736) and (simpos <= 82108)):
        si = 'ACIS-S'
    elif ((simpos >= -86147) and (simpos <= -20000)):
        si = ' HRC-I'
    elif ((simpos >= -104362) and (simpos <= -86148)):
        si = ' HRC-S'
    else:
        si = '  NONE'
    return si