#P181B. Number of Triplets
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ID: 8896
Type: RemoteJudge
2000ms
256MiB
Tried: 0
Accepted: 0
Difficulty: 4
Uploaded By:
Hydro
Tags> Number of Triplets
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.
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 xi, yi ( - 1000 ≤ xi, yi ≤ 1000).
It is guaranteed that all given points are different.
Print the single number — the answer to the problem.
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 xi, yi ( - 1000 ≤ xi, yi ≤ 1000).
It is guaranteed that all given points are different.
Output
Print the single number — the answer to the problem.
3
1 1
2 2
3 3
3
0 0
-1 0
0 1
1
0