Today I was try to solve this problem: https://mirror.codeforces.com/gym/100952/problem/J.

My main idea is:

• Find all point $$$X$$$s that $$$X$$$s is a node of $$$A$$$ and in $$$B$$$'s area.

• Find all point $$$X$$$s that $$$X$$$s is a node of $$$B$$$ and in $$$A$$$'s area.

• Find all intersection points of $$$A$$$ and $$$B$$$.

Let call the set of points we found is $$$S$$$, $$$S$$$ will be a convex hull, find the area of $$$S$$$ — the answer of problem.

But somehow I get WA verdict, can anyone help me to find out why, thanks all.

(This is my code: https://ideone.com/8wXu6a.)