n=int(input())
xy=[list(map(int,input().split())) for _ in range(n)]
mat=[[] for i in range(n)]
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
    mat[i].append([d,i,j])
    mat[j].append([d,j,i])

from heapq import heappop,heappush
todo=[]
for i in range(n):
  if mat[i]:
    mat[i].sort(reverse=True)
    heappush(todo,mat[i].pop())

ans=0
seen=[0]*n
while todo:
  d,i,j=heappop(todo)
  if seen[i]==1 or seen[j]==1:
    if seen[i]==0 and mat[i]:
      heappush(todo,mat[i].pop())
    if seen[j]==0 and mat[j]:
      heappush(todo,mat[j].pop())
  elif i==0 or j==0:
    ans+=1
    seen[i]=1
    seen[j]=1
    seen[0]=0
    if seen[i]==0 and mat[i]:
      heappush(todo,mat[i].pop())
  else:
    seen[i]=1
    seen[j]=1
print(ans)