import sys
from collections import defaultdict

def main():
    n = int(sys.stdin.readline())
    grid_map = defaultdict(list)
    count = 0

    for _ in range(n):
        x, y = map(int, sys.stdin.readline().split())
        cell_x = x // 20
        cell_y = y // 20
        valid = True

        # Check adjacent cells (including current)
        for dx in (-1, 0, 1):
            for dy in (-1, 0, 1):
                adj_cell_x = cell_x + dx
                adj_cell_y = cell_y + dy
                # Check each coin in the adjacent cell
                for (ox, oy) in grid_map.get((adj_cell_x, adj_cell_y), []):
                    dx_p = x - ox
                    dy_p = y - oy
                    dist_sq = dx_p * dx_p + dy_p * dy_p
                    if dist_sq < 400:
                        valid = False
                        break  # Break out of the current for-loop over coins
                if not valid:
                    break  # Break out of dy loop
            if not valid:
                break  # Break out of dx loop

        if valid:
            grid_map[(cell_x, cell_y)].append((x, y))
            count += 1

    print(count)

if __name__ == '__main__':
    main()