#BZOJ3102. Sgu512 Friendly Points

Sgu512 Friendly Points

No submission language available for this problem.

题目描述


Consider n distinct points on a plane.

Two points from that set are said to be friends, when there exists a rectangle with sides parallel to coordinate axes that contains those two points and doesn't contain any other point from the given set. A rectangle is said to contain a point if the point lies within the rectangle or on its border.

How many pairs of friends are there among the given points?

求这样的点对个数:以两点连线为对角线的矩形内不存在其他点(也不能在边界上)

输入格式

The first line of the input file contains an integer n,1<=N<=100 000.

The next n lines contain two integers each, the coordinates of the given points. The coordinates don't exceed 109 by absolute value.

输出格式

 
Output one integer number — the sought number of pairs of friends.
5 0 0 0 2 2 0 2 2 1 1
8