using System;
using System.Collections.Generic;

namespace Ichiendama
{
    class Ichiendama
    {
        public static int Radius = 10;

        private int _x;
        private int _y;

        public int X { get { return _x; } }
        public int Y { get { return _y; } }


        public Ichiendama(int x, int y)
        {
            _x = x;
            _y = y;
        }
        // 2乗距離を返す
        public static double Distance2(Ichiendama a, Ichiendama b)
        {
            return (Math.Pow(a.X - b.X, 2.0) + Math.Pow(a.Y - b.Y, 2.0));
        }
        // 重なっていればtrueを返す
        public static bool CheckOverlap(Ichiendama a, Ichiendama b)
        {
            if (Ichiendama.Distance2(a, b) < Math.Pow(Ichiendama.Radius * 2, 2.0))
            {
                return true;
            }
            else
            {
                return false;
            }
        }

    }

    class Program
    {
        static void Main(string[] args)
        {

            int N = int.Parse(Console.ReadLine());
            int M = 2001;
            int ans = 0;
            List<Ichiendama>[,] Valids = new List<Ichiendama>[M, M];
            for (int i = 0; i < M; i++)
            {
                for (int j = 0; j < M; j++)
                {
                    Valids[i, j] = new List<Ichiendama>();
                }
            }

            char[] delimiter = { ' ' };
            for (int i = 0; i < N; i++)
            {
                string[] s = Console.ReadLine().Split(delimiter);
                int[] xy = { int.Parse(s[0]), int.Parse(s[1]) };
                Ichiendama newcoin = new Ichiendama(xy[0], xy[1]);
                bool isOverlap = false;
                int nx = xy[0]/10;
                int ny = xy[1]/10;
                for (int dx = Math.Max(nx - 2, 0); dx <= Math.Min(nx + 2, M-1); dx++)
                {
                    for (int dy = Math.Max(ny - 2, 0); dy <= Math.Min(ny + 2, M-1); dy++)
                    {
                        foreach (Ichiendama v in Valids[dx, dy])
                        {
                            if (Ichiendama.CheckOverlap(v, newcoin))
                            {
                                isOverlap = true;
                                break;
                            }
                        }
                    }
                }
                if (isOverlap == false)
                {
                    Valids[nx, ny].Add(newcoin);
                    ans++;
                }

            }
            Console.WriteLine(ans);
        }
    }
}