I want to find the convex hull of a set of points so I have been trying to understand the output of the QHull program(http://www.qhull.org/). I gave the co-ordinates of a square 2 # dimension

4 # number of points

$(-1 ,1),( 1, 1),(-1 -1),(1 ,-1)$ and the output that I got was

The first line : 4

Remaining lines: $(2,1,0),(2,2,0),(2,3,1),(2,3,2)$.

I am trying to do the same using Petricht's implementation of QHull(http://lpetrich.org/Science/ computational geometry section) in mathematica but I do not understand the output formats of the two. Petricht's implementation gives:

 CH2QuickHull[{{-1,-1},{-1,1},{1,-1},{1,1}}]


Output: {1,3,4,2}

Can somebody please explain the two outputs ?