import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for(int i=0;i<a.length;i++){
            a[i]=in.nextInt();
        }
        int count=0,count1=0;
        Arrays.sort(a);
        for(int i=0;i<a.length;i++){
           count=0;
           for(int j=i+1;j<a.length;j++){
              // System.out.println(a[i]+" "+a[j]+" "+(a[i]-a[j]));
               if(Math.abs(a[i]-a[j])<=1){
                   count++;
               }
               else{
                   break;
               }
           }
         //  System.out.println("\n"+count+"\n");
           if(count>count1){
               count1=count;
           }
          //  System.out.println("\n\\n");
           
        }
        System.out.println(count1+1);
    }
}