Why is it always ccw? How should I aproach this problem in order to
solve it?


    Thanks!

It's cheat.
now it can't get ac.
You should do with the first and the second coordinat.

I can see that with 2 it can be solved for convex polygons, but for
not convex?

Sorry.
actually,it is 3 coords. I add another coordinate myself.

> I can see that with 2 it can be solved for convex polygons, but for
> not convex?
so just find convex hull , and solve it by that method