#描述#
Given three points P1(x1,y1),P2(x2,y2),P3(x3,y3) , you are to calculate the area surrounded by the three points. If the three points are collinear, the area is zero.

#格式#
##输入格式##
The input file contains several test case, each test case consists of six integers x1,y1,x2,y2,x3,y3, (0&lt=xi&lt=10000 and 0&lt=yi&lt=10000)which are the coordinates of the triangle’s three vertexes. Process to the end of the file.

##输出格式##
For each test case, output a line the area of the corresponding triangle,which should be printed accurately rounded to two decimals.

#样例1#
##样例输入1##

1 1 2 2 3 3
0 0 2 0 0 3

##样例输出1##

0.00
3.00

#限制#
1000ms
32768KB

#提示#

#来源#
Limitfan