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();
        }
        in.close();
        Arrays.sort(a);
        
        
        
        
        int max = 2;
        int begin = 0;
        int end = 0;
        while (begin < n) {
            end = begin+1;
            while (end < n) {
                int diff = a[end]-a[begin];
                if (diff <= 1) {
                    end++;
                    continue;
                }
                int current = end-begin;
                if (current > max) {
                    max = current;
                }
                break;
            }
            if (end == n) {
//                System.out.println(end + " - " + begin);
                int current = end-begin;
                if (current > max) {
                    max = current;
                }
                break;
            }
            begin++;
        }
        
        
        System.out.println(max);
    }
}