import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
//1 3 3 4 5 6
       

public class Solution {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        int count = 0; 
        HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        Arrays.sort(a);
        int j = 0;
        int max = 0;
        for (int a_i=0; a_i<n-1; a_i++) {
            //System.out.println(a[a_i] + " " + a[a_i+1] + " " + a[j]);
            if (Math.abs(a[a_i]-a[a_i+1]) <= 1 && Math.abs(a[j]-a[a_i+1]) <= 1) {
               count++;
               if (count > max) max = count;
            } else {
                j=a_i+1;
                count=0;
            }
        }
        //1 3 3 4 5 6
        System.out.println(max+1);
    }
}