CF749B.Parallelogram is Back

Long time ago Alex created an interesting problem about parallelogram. The input data for this problem contained four integer points on the Cartesian plane, that defined the set of vertices of some non-degenerate (positive area) parallelogram. Points not necessary were given in the order of clockwise or counterclockwise traversal.

Alex had very nice test for this problem, but is somehow happened that the last line of the input was lost and now he has only three out of four points of the original parallelogram. He remembers that test was so good that he asks you to restore it given only these three points.

很久以前，Alex 创建了一个关于平行四边形的有趣问题。该问题的输入数据包含笛卡尔平面上的四个整数点，它们构成了某个非退化（面积为正）平行四边形的顶点集合。这些点未必按顺时针或逆时针顺序给出。

Alex 为此问题准备了一个非常优秀的测试用例，但不知何故，输入的最后一行丢失了，因此他现在只剩下原始平行四边形的四个点中的三个。他记得该测试用例非常优秀，因此请求你仅根据这三个点将其恢复。

The input consists of three lines, each containing a pair of integer coordinates x__i and y__i ( - 1000 ≤ x__i, y__i ≤ 1000). It's guaranteed that these three points do not lie on the same line and no two of them coincide.

输入包含三行，每行包含一对整数坐标 $x_i$ 和 $y_i$（$-1000 \le x_i, y_i \le 1000$）。保证这三个点不共线，且任意两点不重合。

First print integer k — the number of ways to add one new integer point such that the obtained set defines some parallelogram of positive area. There is no requirement for the points to be arranged in any special order (like traversal), they just define the set of vertices.

Then print k lines, each containing a pair of integer — possible coordinates of the fourth point.

首先输出一个整数 $k$ —— 表示添加一个新整数点，使得所得点集构成某个面积为正的平行四边形的方法数。对这些点的排列顺序（例如遍历顺序）没有任何特殊要求，它们仅用于定义顶点集合。

然后输出 $k$ 行，每行包含一对整数 —— 即可能的第四个点的坐标。

If you need clarification of what parallelogram is, please check Wikipedia page:

https://en.wikipedia.org/wiki/Parallelogram

如果需要了解平行四边形的定义，请参阅维基百科页面：

https://en.wikipedia.org/wiki/Parallelogram