P4166 [SCOI2007] Maximum Land Area

On a piece of planar land, there are $N$ points. You may choose any four of them to enclose the land. Of course, you want the polygon formed by these four points to have the maximum area.

The first line contains a positive integer $N$. The next $N$ lines each contain $2$ numbers $x, y$, representing the $x$-coordinate and $y$-coordinate of the point.

Output the maximum polygon area, rounded to $3$ decimal places.

$5\le N\le 2000, 0\le |x|,|y|\le 100000$. Translated by ChatGPT 5