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);
        Array.Sort(a);
        int max = 0;
        for (int i = 0; i < n-1; i++){
            int count = 1;
            for (int j = i+1; j < n; j++){
                int diff = a[j]-a[i];
                if (diff > 1)
                    break;
                count++;
            }
            max = Math.Max(max,count);
        }
        Console.WriteLine(max);
    }
}