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[] b = new int[101];
        
        for(int i=0;i<n;i++)
        b[a[i]]++;
        

        int max=0;
        for(int i=0;i<100;i++)
        if(b[i]+b[i+1]>max)
        {
            max = b[i]+b[i+1];
        }
            
        Console.WriteLine(max);
    }
}