range3 = range(3)

def lap(bin, x, y, dx, dy):
    for xx in range3:
        for yy in range3:
            for bx, by in bin[dx + xx][dy + yy]:
                if (bx - x) ** 2 + (by - y) ** 2 < 400:
                    return True
    bin[dx + 1][dy + 1].append((x, y))
    return False


def solve(XY):
    bin = [[[] for j in range(1003)] for i in range(1003)]

    count = 0
    for x, y in XY:
        dx = x // 20
        dy = y // 20
        if not lap(bin, x, y, dx, dy):
            count += 1

    return count


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

    print(solve(XY))


if __name__ == '__main__':
    main()