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 = -1;
        int[] counts = new int[101];
        counts[a[0]]++;
        for(int i = 1; i < a.length; i++){
            //if(Math.abs(a[i] - a[i-1]) <= 1){
                counts[a[i]]++;
            //}else{               
              //  counts[a[i]] = 1;
            //}
           
            if(a[i]-2 >= 0){
                max = Math.max(max,Math.max(counts[a[i]-2] + counts[a[i]-1], counts[a[i]-1] + counts[a[i]]));
            }else{
                max = Math.max(max,counts[a[i]-1] + counts[a[i]]);
            }
            
        }
        System.out.println(max);
    }
}