A1330.[COCI-2007_2008-contest2]#4 PRAVOKUTNI

N points are placed in the coordinate plane.
Write a program which calculates in how many ways a right triangle can be formed by three of the given points. A right triangle is one in which one of the angles is 90 degrees.

The first line of input contains an integer N (3 ≤ N ≤ 1500), the number of points.
Each of the following N lines contains the coordinates of one point, two integers separated by a space.
The coordinates will be between −109 and 10
9.
No two points will be located at the same coordinates.

Output the number of right triangles.