placed = set()
X0 = [(0, 9), (1, 9), (2, 9), (3, 9), (4, 9), (4, 8), (5, 8), (5, 7), (6, 7),
      (7, 7), (7, 6), (7, 5), (8, 5), (8, 4), (9, 1), (9, 2), (9, 3), (9, 4)]
X1 = X0[:]
for x, y in X0:
    X1.append((-x, y))
    X1.append((x, -y))
    X1.append((-x, -y))
W = 20050
placed = set()
ans = 0
for _ in range(int(input())):
    x, y = map(int, input().split())
    x += 10
    y += 10
    f = False
    for dx, dy in X1:
        if (x + dx) * W + y + dy in placed:
            f = True
            break
        if f:
            break
    else:
        ans += 1
        for dx, dy in X1:
            placed.add((x + dx) * W + y + dy)
print(ans)