import java.util.*;

public class Main {
    static class Point {
        int x;
        int y;

        Point(int x, int y) {
            this.x = x;
            this.y = y;
        }

        double dist(Point o) {
            return Math.sqrt((this.x - o.x) * (this.x - o.x) + (this.y - o.y) * (this.y - o.y));
        }

        @Override
        public String toString() {
            return "(" + this.x + ", " + this.y + ")";
        }
    }

    static int getId(int x, int y) {
        return x * 1001 + y;
    }

    static int[] dirx = new int[]{0, 1, 0, -1, 0, 1, 1, -1, -1};
    static int[] diry = new int[]{0, 0, 1, 0, -1, 1, -1, 1, -1};

    public static void main(String[] argv) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int res = 0;
        Map<Integer, List<Point>> data = new HashMap<Integer, List<Point>>();
        for (int i = 0; i < n; i++) {
            int x = scanner.nextInt();
            int y = scanner.nextInt();
            Point p = new Point(x, y);
            x /= 20;
            y /= 20;
            boolean overwrap = false;
            for (int j = 0; j < dirx.length; j++) {
                int nx = dirx[j] + x;
                int ny = diry[j] + y;
                if (nx < 0 || ny < 0 || nx > 1001 || ny > 1001) continue;
                int newKey = getId(nx, ny);
                if (data.containsKey(newKey)) {
                    List<Point> points = data.get(newKey);
                    for (Point p2 : points) {
//                        System.out.println("compare:" + p.toString() + " : " + p2.toString());
                        if (p.dist(p2) < 20) {
//                            System.out.println("overwrap!!");
                            overwrap = true;
                            break;
                        }
                    }
                }
                if (overwrap) {
                    break;
                }
            }
            if (!overwrap) {
                List<Point> list;
                int id = getId(x, y);
                if (data.containsKey(id)) {
                    list = data.get(id);
                } else {
                    list = new ArrayList<Point>();
                    data.put(id, list);
                }
//                System.out.println("add:" + id + ":" + p.toString());
                res++;
                list.add(p);
            }
        }
        System.out.println(res);
    }
}