using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution
{

    static void Main(String[] args)
    {
        int n = Convert.ToInt32(Console.ReadLine());
        string[] a_temp = Console.ReadLine().Split(' ');
        int[] a = Array.ConvertAll(a_temp, Int32.Parse);
        Console.WriteLine(FindMaxDiff(a));
    }

    static int FindMaxDiff(int[] a)
    {
        int diffMax = 0;
        List<int> diff = new List<int>();
        Array.Sort(a);
        diff.Add(a[0]);
        for (int i = 1; i < a.Length; i++)
        {
            if ((a[i] == diff.First()) || (a[i] == diff.First() + 1))
            {
                diff.Add(a[i]);
            }
            else
            {
                if (diff.Count > diffMax)
                    diffMax = diff.Count;
                diff.Clear();
                diff.Add(a[i]);
            }

                
                
        }

        if (diff.Count > diffMax)
            diffMax = diff.Count;

        return diffMax;

    }
}