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 b[] = new int[101];
        
        for(int a_i=0; a_i < n; a_i++){
            
            b[in.nextInt()]++;
        }
        
        int sum=0;
        
        for(int i=1;i<100;i++){
            
            if(sum<(b[i]+b[i+1]))
                sum=b[i]+b[i+1];
        }

        System.out.println(sum);
    }
}