import math
N=int(input())
A=[];D={};E={};F={}
for i in range(N):
  x,y=map(int, input().split())
  A.append((x,y))
  
  
cc=0
for i in range(N-1):
  for j in range(i+1,N):
    cc+=1
    ax,ay=A[i];bx,by=A[j]
    #x,y:中点
    x,y=(ax+bx),(ay+by)
    xx,yy=ax-bx,ay-by 
    if xx==0:
      if (x,y) not in E:
        E[(x,y)]=0
      E[x,y]+=1
    elif yy==0:
      if (x,y) not in F:
        F[(x,y)]=0
      F[x,y]+=1
    else:
      c=math.gcd(abs(xx),abs(yy))
      xx//=c;yy//=c
      if xx<0:
        xx*=-1;yy*=-1 
      if (xx,yy,x,y) not in D:
        D[(xx,yy,x,y)]=0
      D[(xx,yy,x,y)]+=1 


ansa=0
for x,y in E:
  if (x,y) in F:
    ansa+=E[(x,y)]*F[(x,y)]

ansb=0
for xx,yy,x,y in D:
  p,q=-yy,xx
  if p<0:
    p*=-1;q*=-1 
  if (p,q,x,y) in D:
    ansb+=D[(p,q,x,y)]*D[(xx,yy,x,y)]
print(ansa+ansb//2)