n=int(input())
p=[]
for i in range(n):
  x,y=map(int,input().split())
  p+=[(x,y)]
from math import gcd
p.sort()
l={}
for i in range(n-1):
  for j in range(i+1,n):
    sx,sy=p[i]
    tx,ty=p[j]
    mx,my=sx+tx,sy+ty
    dx,dy=tx-sx,ty-sy
    if dx==0:
      dy=1
    elif dy==0:
      dx=1
    else:
      g=gcd(abs(dx),abs(dy))
      dx//=g
      dy//=g
    v=(mx,my,dx,dy)
    if v not in l:
      l[v]=0
    l[v]+=1
g=0
for a in l:
  mx,my,dx,dy=a
  if dx<=0:
    continue
  if dy<0:
    continue
  if dy==0:
    b=(mx,my,0,1)
  else:
    b=(mx,my,dy,-dx)
  if b in l:
    g+=l[a]*l[b]
print(g)