Number of Triplets

2000ms

262144K

Description:

You are given n points on a plane. All points are different.

Find the number of different groups of three points (A, B, C) such that point B is the middle of segment AC.

The groups of three points are considered unordered, that is, if point B is the middle of segment AC, then groups (A, B, C) and (C, B, A) are considered the same.

Input:

The first line contains a single integer n (3 ≤ n ≤ 3000) — the number of points.

Next n lines contain the points. The i-th line contains coordinates of the i-th point: two space-separated integers x_i, y_i ( - 1000 ≤ x_i, y_i ≤ 1000).

It is guaranteed that all given points are different.

Output:

Print the single number — the answer to the problem.

Sample Input:

Sample Output:

Sample Input:

Sample Output:

Informação

Provedor Codeforces

Código CF181B