import math

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

count = 0

for i in range(1, n):
    x1, y1 = balloons[0]
    xi, yi = balloons[i]
    dx = xi - x1
    dy = yi - y1
    t_i = math.hypot(dx, dy) / 2  # distance / 2

    can_remove = False
    for j in range(1, n):
        if j == i:
            continue
        xj, yj = balloons[j]
        dx_ij = xj - xi
        dy_ij = yj - yi
        t_ij = math.hypot(dx_ij, dy_ij) / 2

        dx_j0 = xj - x1
        dy_j0 = yj - y1
        t_j = math.hypot(dx_j0, dy_j0) / 2

        if t_ij < t_i and t_j > t_ij:
            can_remove = True
            break

    if not can_remove:
        count += 1

print(count)