using System;
using System.Collections.Generic;
using System.Text;
using System.Linq;

class Program
{
    public void Proc()
    {
        Reader.IsDebug = false;
        int tyukeiCount = int.Parse(Reader.ReadLine());
        List<Pos> tyukeiList = new List<Pos>();
        for (int i = 0; i < tyukeiCount; i++)
        {
            tyukeiList.Add(new Pos(Reader.GetInt()));
        }

        if (tyukeiList.Count == 0)
        {
            Console.WriteLine(1);
            return;
        }
        else if (tyukeiList.Count == 1)
        {
            Console.WriteLine(2);
            return;
        }


        long maxLen2 = 0;
        List<List<Pos>> groupList = new List<List<Pos>>();
        foreach (Pos pos in tyukeiList)
        {
            List<Pos> tmp = new List<Pos>(tyukeiList.FindAll(a=> ((pos.X - a.X)*(pos.X - a.X)+(pos.Y - a.Y)*(pos.Y - a.Y)) <= 100));
            List<List<Pos>> mergeList = new List<List<Pos>>();
            List<Pos> otherList = new List<Pos>();
            tmp.ForEach((a) => {
                bool grouped = false;
                groupList.ForEach((b) =>
                {
                    if (b.Contains(a))
                    {
                        grouped = true;
                        if (!mergeList.Contains(b))
                        {
                            mergeList.Add(b);
                        }
                    }
                });
                if (!grouped)
                {
                    otherList.Add(a);
                }
            });
            mergeList.ForEach((a) => {
                groupList.Remove(a);
                otherList.AddRange(a);
            });
            if (otherList.Count > 0)
            {
                groupList.Add(otherList);
            }
        }
        groupList.ForEach(a => maxLen2 = Math.Max(maxLen2, GetLen2(a)));
        double ans = 2;
        if (maxLen2 > 0)
        {
            ans = Math.Sqrt(maxLen2) + 2;
        }
        Console.WriteLine(ans.ToString("#################################0.#############"));

    }

    private long GetLen2(List<Pos> src)
    {
        List<Pos> target = new List<Pos>();
        List<Pos> work = new List<Pos>(src.OrderBy(a=>a.X));
        for (int i = 0; i < Math.Min(5, work.Count); i++)
        {
            if (!target.Contains(work[i]))
            {
                target.Add(work[i]);
            }
        }
        work.Reverse();
        for (int i = 0; i < Math.Min(5, work.Count); i++)
        {
            if (!target.Contains(work[i]))
            {
                target.Add(work[i]);
            }
        }
        work = new List<Pos>(src.OrderBy(a => a.Y));
        for (int i = 0; i < Math.Min(5, work.Count); i++)
        {
            if (!target.Contains(work[i]))
            {
                target.Add(work[i]);
            }
        }
        work.Reverse();
        for (int i = 0; i < Math.Min(5, work.Count); i++)
        {
            if (!target.Contains(work[i]))
            {
                target.Add(work[i]);
            }
        }
        work = new List<Pos>(src.OrderBy(a => Math.Abs(a.X) + Math.Abs(a.Y)));
        for (int i = 0; i < Math.Min(5, work.Count); i++)
        {
            if (!target.Contains(work[i]))
            {
                target.Add(work[i]);
            }
        }
        work.Reverse();
        for (int i = 0; i < Math.Min(5, work.Count); i++)
        {
            if (!target.Contains(work[i]))
            {
                target.Add(work[i]);
            }
        }
        long ans = 0;
        for (int i = 0; i < target.Count - 1; i++)
        {
            for (int j = i + 1; j < target.Count; j++)
            {
                long tmp = (target[i].X - target[j].X) * (target[i].X - target[j].X);
                tmp += (target[i].Y - target[j].Y) * (target[i].Y - target[j].Y);
                ans = Math.Max(ans, tmp);
            }
        }
        return ans;
    }

    public class Pos
    {
        public long X;
        public long Y;
        public Pos(int[] pos)
        {
            this.X = pos[0];
            this.Y = pos[1];
        }
    }

    public class Reader
    {
        public static bool IsDebug = true;
        private static String PlainInput = @"



2
3 3
12 1



 
";
        private static System.IO.StringReader Sr = null;
        public static string ReadLine()
        {
            if (IsDebug)
            {
                if (Sr == null)
                {
                    Sr = new System.IO.StringReader(PlainInput.Trim());
                }
                return Sr.ReadLine();
            }
            else
            {
                return Console.ReadLine();
            }
        }
        public static int[] GetInt(char delimiter = ' ', bool trim = false)
        {
            string inptStr = ReadLine();
            if (trim)
            {
                inptStr = inptStr.Trim();
            }
            string[] inpt = inptStr.Split(delimiter);
            int[] ret = new int[inpt.Length];
            for (int i = 0; i < inpt.Length; i++)
            {
                ret[i] = int.Parse(inpt[i]);
            }
            return ret;
        }
    }
    static void Main()
    {
        Program prg = new Program();
        prg.Proc();
    }
}