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.
Output
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.
Note
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.