Area = ?

Problem Statement

Given four coordinate points $(X_1,Y_1,X_2,Y_2,X_3,Y_3,X_4,Y_4)$ you are asked to find the area of this quadrilateral, which might be

• square
• rectangle
• Parallelograms
• trapezoid
• rhombus

Constraints

• $0 \leq X_1, Y_1, X_2, Y_2, X_3, Y_3,X_4,Y_4 \leq 1000$
• The four points $A$, $B$, $C$and $D$ are not collinear.
• All input values are integers.

Standard input

The input is given from Standard Input in the following format:

$X_1,Y_1$ $X_2,Y_2$ $X_3,Y_3$ $X_4,Y_4$

Output

Given four coordinate points $(X_1,Y_1,X_2,Y_2,X_3,Y_3,X_4,Y_4)$ you are asked to find the area of this quadrilateral

Sample calendar

Sample Input 1

0 2
0 0
2 2
2 0

Sample Output 1

4

Sample Input 2

0 0
4 0
3 2
1 2

Sample Output 2

6

题面翻译

给定四个坐标点 $(X_1,Y_1,X_2,Y_2,X_3,Y_3,X_4,Y_4)$，要求你找出这个四边形的面积