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];
        int[] ar=new int[100];
        int max=0;
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
            if(a[a_i]>max)
            	max=a[a_i];
        }
        for(int i=0;i<n;i++){
            ar[a[i]]++;
        }
        int sum=0;
        for(int i=0;i<ar.length-1;i++){
        	
            if(ar[i]+ar[i+1]>sum)
                sum=ar[i]+ar[i+1];
            else if(ar[i]>1 && ar[i]>sum)
                sum=ar[i];
        }
        System.out.println(sum);
    }
}