COCI '07 Contest 2 #6 Pravokutni

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Points: 10
Time limit: 0.4s
Memory limit: 32M

Problem types

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.

Input Specification

The first line of input contains an integer N (3 \le N \le 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 -10^9 and 10^9.

No two points will be located at the same coordinates.

Output Specification

Output the number of right triangles.

Sample Input 1

3
4 2
2 1
1 3

Sample Output 1

1

Sample Input 2

4
5 0
2 6
8 6
5 7

Sample Output 2

0

Sample Input 3

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

Sample Output 3

7

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