def main():

    def check(x, y):
        for dy in range(-1, 2):
            for dx in range(-1, 2):
                bx, by = x // size + dx, y // size + dy
                if 0 <= bx < 20000 // size + 1 and 0 <= by < 20000 //size + 1:
                    for cx, cy in L[bx][by]:
                        if (x-cx)**2 + (y-cy)**2 < 400:
                            return False;
        return True;


    n = int(input())
    size = 50
    L = [[[] for i in range(20000 // size + 1)] for j in range(20000 // size + 1)]

    ans = 0
    for i in range(n):
        x, y = map(int, input().split())
        if check(x, y):
            ans += 1
            L[x//size][y//size].append((x, y))
    print(ans)


if __name__ == '__main__':
    main()