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[]c=new int[100];
        for(int i=0;i<100;i++)
            c[i]=0;
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
            c[a[a_i]]+=1;
        }
        int m=0;
        for(int i=1;i<99;i++){
            if(c[i]+c[i+1]>m)
                m=c[i]+c[i+1];
        }
        System.out.print(m);
    }
}