from heapq import *

N=int(input())
point=[tuple(map(int,input().split())) for _ in range(N)]

d=set()
res=0
for i in range(1,N):
    que=[]
    heapify(que)
    for j in range(N):
        if i==j:
            continue
        xi,yi=point[i]
        xj,yj=point[j]
        dist=((xi-xj)**2+(yi-yj)**2)**0.5
        heappush(que,(dist,j))
    while(que[0][1] in d):
        heappop(que)
    if que[0][1]==0:
        d.add(i)
        res+=1
print(res)