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];
       // Map<Integer,Integer> m = new HashMap<Integer,Integer>();
       
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
            //System.out.println("Failed in if");
            //if (m.containsKey((Integer) a[a_i])){
             //  m.put(a[a_i],(int) m.get(a_i)+1);
              
           // }
           // else{
                //System.out.println("Failed in else");
               // m.put(a[a_i],1);
           // }
        }
       //System.out.println("reached here");
        //Arrays.sort(a);
        int maxLength = 1;
      
        for (int i = 0; i < n; i++){
            int lengthOne = 1;
            int lengthTwo = 1;
            for (int j = 0; j < n; j++){
                if ( i != j ){
                  if (a[i] + 1 == a[j])
                     lengthOne++;
                  if (a[i] - 1 == a[j])
                      lengthTwo++;
                  if (a[i] == a[j]){
                      lengthOne++;
                      lengthTwo++;
                  }
            }
            }
            int currentMaxSize = Math.max(lengthOne,lengthTwo);
            maxLength = Math.max(currentMaxSize,maxLength);
            
        }
                    
          
            
        
     
       System.out.println(maxLength);
        
    }
}