Point3d is not callable

import Rhino
import scriptcontext
import System
import Rhino.UI
import Eto.Drawing as drawing
import Eto.Forms as forms
import rhinoscriptsyntax as  rs
A = rs.GetObject("SELECT OBJECT", 8 + 16)
box = rs.BoundingBox(A)
LP=(box(0)(0))- (box(1)(0))
print LP

square brackets instead of parentheses.