from collections import defaultdict


def lap(bin, x, y, dx, dy):

    cs = []
    for xx in [-1, 0, 1]:
        for yy in [-1, 0, 1]:
            cs.extend(bin[dx + xx, dy + yy])

    for bx, by in cs:
        if (bx - x) ** 2 + (by - y) ** 2 < 400:
            return True

    for xx in [-1, 0, 1]:
        for yy in [-1, 0, 1]:
            bin[dx + xx, dy + yy].append((x, y))

    return False


def solve(XY):
    bin = defaultdict(list)

    count = 0
    for x, y in XY:
        dx = x // 10
        dy = y // 10
        if not lap(bin, x, y, dx, dy):
            count += 1

    return count


def main():
    N = int(input())
    XY = [list(map(int, input().split())) for i in range(N)]

    print(solve(XY))


if __name__ == '__main__':
    main()