You are given n points on a plane. All the points are distinct and no three of them lie on the same line. Find the number of parallelograms with the vertices at the given points.

-----Input-----

The first line of the input contains integer n (1 ≤ n ≤ 2000) — the number of points.

Each of the next n lines contains two integers (x_{i}, y_{i}) (0 ≤ x_{i}, y_{i} ≤ 10^9) — the coordinates of the i-th point.

-----Output-----

Print the only integer c — the number of parallelograms with the vertices at the given points.

-----Example----- Input 4 0 1 1 0 1 1 2 0

Output 1