PRAVOKUTNI

문제

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. 

입력

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 10⁹. 

No two points will be located at the same coordinates. 

출력

Output the number of right triangles. 

 

3
4 2
2 1
1 3

1

4
5 0
2 6
8 6
5 7

0

5
-1 1
-1 0
0 0
1 0
1 1

7