Tom works in a company that produces covers for all kinds of holes, such as holes on
streets and wells. He encounters a problem as follows: given a hole H which is a
polygon with interior angles of only 90 or 270 degrees, determine the smallest
rectangular cover that can completely cover H. In this problem, H is given in a
coordinate system such that each of its edges is either vertical or horizontal. When
covering a hole, each edge of the cover should also be either vertical or horizontal in
the same coordinate system.
Consider the example in Figure 1. It is easy to see that the smallest rectangular cover
that can completely cover H is a rectangle of size 4 × 8.

Figure 1: a rectangular hole H.

In this problem, you are asked to find the area of the smallest rectangular cover that can completely cover H. For example, in Figure 1, the output is 32.

Technical Specification

1. The number of the vertices of H, denoted by n, is a positive integer between 4 and 100.
2. The x-coordinates and y-coordinates of vertices are integers between 0 and 1000.

湯姆在一家公司工作，該公司生產各種孔洞的蓋子，例如街道和水井的孔洞。 他遇到以下問題：給定一個孔洞H（該孔洞是一個僅具有90度或270度內角的多邊形），請找出可以完全蓋住H的最小矩形蓋子。在此問題中，H的坐標是由每個邊緣均為垂直或水平的坐標系統表示。覆蓋孔洞時，蓋子的每個邊緣在同一坐標系統中也應為垂直或水平。

考慮圖1中的示例。很容易看出，可以完全覆蓋H的最小矩形蓋子是大小為4 × 8的矩形。

圖1：矩型孔洞H

在此問題中，你被要求找出可以完全覆蓋H的最小矩形蓋子。例如，在圖1中，輸出為32。

特別定義：

1. H的頂點數（用n表示）是4到100之間的正整數。
2. 頂點的x坐標和y坐標是0到1000之間的整數。