I need help explaining the runtime of the the Conves Hull problem known by the name Onion Peeling.

The objective of this problem is to find out the depth of every point in a given point set P consisting of n points.

If anyone can give a detailed explanation

Thanks

The points in the convex hull of Phas depth 0. This means that in the example every point lying on the red polygon has depth 0. Now take away the points which have depth 0. Find out the convex hull of the remaining set of points. In our case, these are the points lying on the green polygon. These points have depth 1. Continuing on like this, one can easily observe that in our example the depth of a point is an integer between 0 and 3. What is the runtime of the above algorithm in Big-Oh notation? Please explain your answer. Without explanation, you will receive zero for this