using System;

namespace No202_1{
    public class Program{
        public static void Main(string[] args){
            var sr = new StreamReader();
            //---------------------------------
            const int H = 20000;
            const int W = 20000;
            var map = new bool[H + 1, W + 1];
            var sum = 0;
            var N = sr.Next<int>();

            Func<int, int, bool> isInside = (x, y) => 0 <= x && x <= W && 0 <= y && y <= H;

            for(var i = 0; i < N; i++){
                var nx = sr.Next<int>();
                var ny = sr.Next<int>();

                var isExist = false;
                for(var y = -20; y <= 20; y++){
                    for(var x = -20; x <= 20; x++){
                        isExist |= isInside(ny + y, nx + x) && map[ny + y, nx + x] && x * x + y * y < 400;
                    }
                }

                if(!isExist){
                    sum++;
                    map[ny, nx] = true;
                }
            }

            Console.WriteLine(sum);
            //---------------------------------
        }
    }

    public class StreamReader{
        private readonly char[] _c = {' '};
        private int _index = -1;
        private string[] _input = new string[0];

        public T Next<T>(){
            if(_index == _input.Length - 1){
                _index = -1;
                while(true){
                    string rl = Console.ReadLine();
                    if(rl == null){
                        if(typeof(T).IsClass) return default(T);
                        return (T)typeof(T).GetField("MinValue").GetValue(null);
                    }
                    if(rl != ""){
                        _input = rl.Split(_c, StringSplitOptions.RemoveEmptyEntries);
                        break;
                    }
                }
            }
            return (T)Convert.ChangeType(_input[++_index], typeof(T), System.Globalization.CultureInfo.InvariantCulture);
        }
    }
}