import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

from math import gcd
def f(x1, y1, x2, y2):
    a = y2 - y1
    b = - (x2 - x1)
    c = -x1 * y2 + x2 * y1
    g = gcd(a, gcd(b, c))
    a //= g
    b //= g
    c //= g
    if (a, b, c) < (-a, -b, -c):
        a, b, c = -a, -b, -c
    return a, b, c

n = ni()
p = [na() for _ in range(n)]

from collections import defaultdict

d = defaultdict(int)
c = defaultdict(int)
for i in range(n):
    for j in range(i+1, n):
        x1, y1 = p[i]
        x2, y2 = p[j]
        dx, dy = x2 - x1, y2 - y1
        if (dx, dy) < (-dx, -dy):
            dx, dy = -dx, -dy
        g = gcd(dx, dy)
        d[(x1+x2, y1+y2, dx // g, dy // g)] += 1
ans = 0
#print(d)
for x, y, dx, dy in list(d.keys()):
    DX, DY = dy, -dx
    if (DX, DY) < (-DX, -DY):
        DX, DY = -DX, -DY
    ans += d[(x, y, DX, DY)] * d[(x, y, dx, dy)]
print(ans//2)