Virtual contest is a way to take part in past contest, as close as possible to participation on time. It is supported only ACM-ICPC mode for virtual contests.
If you've seen these problems, a virtual contest is not for you - solve these problems in the archive.
If you just want to solve some problem from a contest, a virtual contest is not for you - solve this problem in the archive.
Never use someone else's code, read the tutorials or communicate with other person during a virtual contest.

No tag edit access

D. Number of Parallelograms

time limit per test

4 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputYou 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

Codeforces (c) Copyright 2010-2017 Mike Mirzayanov

The only programming contests Web 2.0 platform

Server time: Mar/26/2017 21:51:38 (c2).

Desktop version, switch to mobile version.
User lists

Name |
---|