N = int(input())
XY = [list(map(int, input().split())) for _ in range(N)]
D = []

for i in range(N - 1):
    x1, y1 = XY[i]
    for j in range(i + 1, N):
        x2, y2 = XY[j]
        d2 = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2)
        D.append((d2, i, j))
D.sort(key = lambda x:x[0])
cnt = 0
removed = [0] * N
for d, i, j in D:
    if removed[i] or removed[j]:
        continue
    if i == 0:
        removed[j] = 1
        cnt += 1
    else:
        removed[i] = 1
        removed[j] = 1
print(cnt)