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) {
        int d=0;
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        ArrayList<Integer> a = new ArrayList<Integer>(n);
        for(int a_i=0; a_i < n; a_i++){
             a.add(in.nextInt());
        } 
        
       Collections.sort(a);
        
        for(int i=0;i<n-1;i++)
            {
            int c=0;
            int key=a.get(i);
           
            int j=i+1;
            while( j<n&&(a.get(j)-key==0 || a.get(j)-key==1 || a.get(j)-key==-1 ))
            {c++;j++;}
         
         if(d<c)d=c;
          if(j==n)break;
        }
        
        System.out.println(d+1);
        
    }
}