 At each step in this Jarvis's march algorithm, we have a point formula_24 in the convex hull (at the beginning, formula_24 may be the point in formula_1 with the lowest y coordinate, which is guaranted to be in the convex hull of formula_1), and need to find a point formula_28 such that all other points of formula_1 are to the right of the line formula_30, where the notation formula_28 simply means that the next point, that is formula_32, is determined as a function of formula_24 and formula_1.The convex hull of the set formula_16, formula_17, is known and contains at most formula_10 points (listed in a clockwise or counter-clockwise order), which allows to compute formula_38 in formula_39 time by binary search.Hence, the computation of formula_38 for all the formula_20 subsets can be done in formula_42 time.