Description: 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 Format: 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 (xi, yi) (0 ≤ xi, yi ≤ 109) — the coordinates of the i-th point. Output Format: Print the only integer c — the number of parallelograms with the vertices at the given points. Note: None