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);
        //for(int i = 0; i < n; i++){
        //    System.out.print(a[i] + " ");
        //}
        //System.out.println();
        int max_length = 0;        
        for(int i = 0; i < n; i++){
            //start at i
            int j = i + 1;
            while(j < n && (a[j] - a[i] < 2)){
                j++;
            }            
            if(j - i > max_length){
                max_length = j - i;
            }
        }
        System.out.println(max_length);
    }
}