AutoCAD 2013 :: How To Get The Area Of Polyline

how to get the area of this polyline .........  

i used properties command >>>

i used li command >>>

i used area then o command >>>> it says that area = 362.5350 ok this is wrong .. 

i calculate the area of the polyline by separating it to parts then subtract the area >>> 368.62 - 7.79 =     360.83  this is the correct area 

actually this is to hard to separate polyline to parts, when i have alot of polyline.

i guess this problem causes, when you have self-intersecting polylines the file is attached ..