题目描述
Little smart QiQi is fond of coin tossing. This day, he came to a huge field, where there's a irregular convex swamp within. Little smart QiQi didn’t want to toss the coin into the swamp, and thus, she needed to know the area of this convex. Please help her.
输入格式
The input contains several test cases, ended with EOF. In each test case, an integer N(3≤N≤100) exists first, indicating the number of vertex. The following N lines give the coordinates