## Problem Description

Given n distinct points on a plane, your task is to find the triangle that have the maximum area, whose
vertices are from the given points.

## Input

The input consists of several test cases. The first line of each test case contains an integer n, indicating
the number of points on the plane. Each of the following n lines contains two integer xi and yi, indicating
the ith points. The last line of the input is an integer -1, indicating the end of input, which should not
be processed. You may assume that 1<=n<=50000 and -10^4<=xi,yi<=10^4 for all i=1...n

## Output

For each test case, print a line containing the maximum area, which contains two digits after the decimal
point. You may assume that there is always an answer which is greater than zero.

## Sample Input

3
3 4
2 6
2 7
5
2 6
3 9
2 0
8 0
6 5
-1

## Sample Output

0.50
27.00

## Source

Shanghai2004 Preliminary