1083  Union
Time Limit : 10 Second
Memory Limit : 128 MB
Submission: 389
Solved: 138
 Description
 Given two simple polygons, you are asked to calculate the area of their union.
 Input
 There is a single case:
In the first line: two integers n1 and n2, indicating the number of the vertex of the two polygons(3 <= n1, n2 <= 500).
In the following n1 lines: each line contains two integers xi and yi, the coordinate of the ith vertex of the first polygon.
In the following n2 lines: each line contains two integers xi and yi, the coordinate of the ith vertex of the second polygon.
All the vertices are given in the counterclockwise order.
All the xs and the ys are in the range of [20000, 20000].  Output
 A single number: the area of the union with a precision of two numbers after the decimal point.
 sample input

4 4 1 0 2 0 2 3 1 3 0 1 3 1 3 2 0 2
 sample output

5.00
 hint
 source
 Isun