You are given n points on a plane. All points are different.
Find the number of different groups of three points (A,B,C) such that point B is the middle of segment AC.
The groups of three points are considered unordered, that is, if point B is the middle of segment AC, then groups (A,B,C) and (C,B,A) are considered the same.
The first line contains a single integer n (3≤n≤3000) − the number of points.
Next n lines contain the points. The i-th line contains coordinates of the i-th point: two space-separated integers xi,yi (-1000≤xi,yi≤1000).
It is guaranteed that all given points are different.
Print the single number − the answer to the problem.
3
1 1
2 2
3 3
1
3
0 0
-1 0
0 1
0