PROGRAMMING:Calculate triangle area
###Task description
There is a triangle on the plane. The coordinates of its three vertices are (x1, Y1), (X2, Y2), (X3, Y3). What is the area of the triangle.
###Input format:
Input only one line, including 6 single precision floating-point numbers, corresponding to x1, Y1, X2, Y2, X3, Y3 respectively.
###Output format:
Output is also a line, output triangle area, accurate to two decimal places.
###Input example:
```in
0 0 4 0 0 3
```
###Output example:
```out
six
```
###Tips
Note: this topic is selected from openjudge website http://noi.openjudge.cn/ch0103/17/ .
answer：If there is no answer, please comment
There is a triangle on the plane. The coordinates of its three vertices are (x1, Y1), (X2, Y2), (X3, Y3). What is the area of the triangle.
###Input format:
Input only one line, including 6 single precision floating-point numbers, corresponding to x1, Y1, X2, Y2, X3, Y3 respectively.
###Output format:
Output is also a line, output triangle area, accurate to two decimal places.
###Input example:
```in
0 0 4 0 0 3
```
###Output example:
```out
six
```
###Tips
Note: this topic is selected from openjudge website http://noi.openjudge.cn/ch0103/17/ .
answer：If there is no answer, please comment