the input part says the points will be described in
clockwise order, but later in the sample input part, the
points are given in the counter clockwise order, why?

I think for this one problem,clockwise or counter clockwise
doesnt matter.

> the input part says the points will be described in
> clockwise order, but later in the sample input part, the
> points are given in the counter clockwise order, why?

<--
Well, why are u so sure that OY is directed up? I think, it
is directed down! ;)
But, it really doesn't metter!