CF340B Maximal Area Quadrilateral

Iahub has drawn a set of $ n $ points in the cartesian plane which he calls "special points". A quadrilateral is a simple polygon without self-intersections with four sides (also called edges) and four vertices (also called corners). Please note that a quadrilateral doesn't have to be convex. A special quadrilateral is one which has all four vertices in the set of special points. Given the set of special points, please calculate the maximal area of a special quadrilateral.

The first line contains integer $ n $ ( $ 4

Output a single real number — the maximal area of a special quadrilateral. The answer will be considered correct if its absolute or relative error does't exceed $ 10^{-9} $ .

In the test example we can choose first $ 4 $ points to be the vertices of the quadrilateral. They form a square by side $ 4 $ , so the area is $ 4·4=16 $ .