Rectangles-1

Given n distinct points on the plane. Required to find a number of different non-degenerate rectangles whose vertices are the given points.

Note that the parties sought rectangles may not be parallel to the axes.

Input

In the first line of the input file contains the number n (1 ≤ n ≤ 4063). Followed by n pairs of integers (x_i, y_i) (0 ≤ x_i, y_i ≤ 32000).

Output

Derive the output file a single number - the number of the desired rectangle.

Examples