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 a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        
        Arrays.sort(a);
        int max = 0; 
        for(int i=0; i < n - 1; i++){
            int thisMax = 0;
           for(int j = i+1 ; j < n ; j++){
               if (a[j] - a[i] <= 1){
                   thisMax++;
               }
           }
            if (max < thisMax){
                max = thisMax ;
            }
        }
         if (max > 0){
                max++ ;
            }
        System.out.println(max);
    }
}