import java.util.*;
import java.lang.*;
import java.io.*;
public class PickingNumber
{    //*****************************************    VARIABLE DECLERATION SECTION   ********************************************************************;
         //static ArrayList<Integer> al;
         //static PriorityQueue<Integer> pq;
         //static TreeMap<Integer,Integer> tm;
         //static TreeSet<Integer> ts;
	     //static ArrayList<ArrayList<Integer>>  graph;
         // static int[][] dp;
	//*****************************************    VARIABLE DECLERATION ENDS   ********************************************************************;

    //************************************************   MAIN FUNCTION  *************************************************************************; 
	public static void main(String[] args) 
	{   //al=new ArrayList<Integer>();
		//graph=new ArrayList<ArrayList<Integer>>();op
		//pq=new PriorityQueue<Integer>();
		//ts=new TreeSet<Integer>();
		//tm=new TreeMap<Integer,Integer>();
        //dp=new int[][];
        //System.out.println("");
		 FastReader scan=new FastReader();
         int n=scan.nextInt();
         int[] arr=new int[101];
         Arrays.fill(arr,0);
         for(int i=0;i<n;i++)
            arr[scan.nextInt()]++;
        int res=0;
        for(int i=0;i<=99;i++)
        {
            if(res<arr[i]+arr[i+1])res=arr[i]+arr[i+1];
        }
        System.out.println(res);


		 

	}
	//***********************************************  MAIN FUNCTION ENDS   *********************************************************************;

	//**********************************************   AUXILIARY FUNCTIONS  **********************************************************************;
	/*static void function()
	{

	}*/
	//**********************************************   AUXILIARY FUNCTIONS  ENDS  **********************************************************************;

	//**********************************************   INPUT FUNCTIONS     ******************************************************************************;
       static class FastReader
    {   BufferedReader br;   StringTokenizer st;
        public FastReader()
        {  br = new BufferedReader(new  InputStreamReader(System.in)); }
        String next()
        {    while (st == null || !st.hasMoreElements())
            {    try
                {  st = new StringTokenizer(br.readLine()); }
                catch (IOException  e)
                {  e.printStackTrace(); }
            }
            return st.nextToken();
        }
        int nextInt()
        {   return Integer.parseInt(next()); }
        long nextLong()
        {   return Long.parseLong(next()); }
        double nextDouble()
        {  return Double.parseDouble(next()); }
        String nextLine()
        { String str = "";
            try
            {     str = br.readLine(); }
            catch (IOException e)
            {     e.printStackTrace(); }
            return str;
        }
    }
	//**********************************************   INPUT FUNCTIONS     ******************************************************************************;
}