Problem C: Try Tri (2011-ish)

You have the following task: to find the areas of triangles. The triangles are well behaved, however! Their vertices are all integer coordinates on the XY plane.

input

The input will be a number of lines of inputs, each line representing a triangle. The line will consist of six integers: x₁ y₁ x₂ y₂ x₃ y₃. These represent the three vertices of the triangle: <x₁, y₁>, <x₂, y₂>, and <x₃, y₃>, Each x_k and y_k is between 0 and 10,000, inclusive.

The last line of input consists of a single -1. This indicates the stop.

Sample Input

 0  0 10  0  0 10
 0  0  0 10  1 10
 0 10 10 10 10  0
 0  0 10 10  0 10
 0  0 10 10  0  5
 0  0 10 10  1  5
 0  0  9 10  1  5
 5  0  0 10 10 10
 0  0  5  5 10 10
 0  0 10000 0 0 10000
-1

Output

For each line of input representing a triangle, print a line of output with that triangle's area, with one degree of precision to the right of the decimal point.

Sample Output

50.0
5.0
50.0
50.0
25.0
20.0
17.5
50.0
0.0
50000000.0