n=int(input())
xy=[list(map(int,input().split())) for _ in range(n)]
ary=[]
for i in range(n):
  xi,yi=xy[i]
  for j in range(i):
    xj,yj=xy[j]
    d=(xi-xj)**2+(yi-yj)**2
    ary.append([d,i,j])
ary.sort()
ans=0
mi=set(range(n))
for d,i,j in ary:
  if i in mi and j in mi:
    if i!=0 and j!=0:
      mi.discard(i)
      mi.discard(j)
    else:
      ans+=1
      if j!=0:
        mi.discard(j)
      else:
        mi.discard(i)
print(ans)