Giải bài trực tuyến

Rhombs

A rhomb is a four-sided polygon in which every side has the same length. The rhomb shape appears in the diamonds suit in playing cards, in art patterns, etc. Squares are also special cases of rhombs.

You have to solve a problem about rhombs: given N points in the plane, count the number of rhombs which have four verticles in the given set of points.

Input

• Line 1: a number N that is the number of points (4 ≤ N ≤ 1500).
• The i^th line of the next N lines contains two integers x_i, y_i that are coordinates of the i^th point (-50 ≤ x_i, y_i ≤ 50).

Output

Print a single number that is the number of rhombs that have four verticles in the given set of points.

Example

Input
8
-1 0
0 1
1 0
0 0
1 1
0 -1
1 -1
2 0

Output
4