https://blog.6r33n.kr/posts/%EA%B0%80%EC%9E%A5-%EC%89%BD%EA%B2%8C-%EC%84%A4%EB%AA%85%ED%95%98%EB%8A%94-%EB%B3%BC%EB%A1%9D-%EA%BB%8D%EC%A7%88-convex-hull/