from operator import itemgetter

N = int(input())
XY = [list(map(int, input().split())) for _ in range(N)]
A = [((ax-bx)**2+(ay-by)**2, a, b) for a, (ax, ay) in enumerate(XY) for b, (bx, by) in enumerate(XY[a+1:], a+1)]
A.sort(key=itemgetter(0))
ans = 0
Closed = [False] * N
for _, a, b in A:
    if Closed[a] == Closed[b] == False:
        if a != 0 and b != 0:
            Closed[a] = True
            Closed[b] = True
        elif a == 0:
            Closed[b] = True
            ans += 1
        else:
            Closed[a] = True
            ans += 1
print(ans)