Total Surface Area

Please help to calculate total surface area in Grasshopper.
If geometries are overlapped shown as below, then how can I calculate the surface that is only “exposed to outside”? The overlapping area should NOT be included.

Which component should I use in Grasshopper?

First use Transform->Shape->Solid Union to join them all into one brep, then you can use Surface->Analysis->Area. (112.0 KB)