import sys
input = sys.stdin.readline

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

for i in range(N):
    for j in range(i+1, N):
        xi, yi = xy[i]
        xj, yj = xy[j]
        l.append(((xi-xj)**2+(yi-yj)**2, i, j))

l.sort()
flag = [False]*N
ans = 0

for _, i, j in l:
    if flag[i] or flag[j]:
        continue
    
    if i==0:
        ans += 1
        flag[j] = True
    elif j==0:
        ans += 1
        flag[i] = True
    else:
        flag[i] = True
        flag[j] = True

print(ans)