#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]

number_set = set(a)
max_score = 0

def calculate_score(number, array):
    number_count = a.count(number)
    
    number_minus_count = a.count(number - 1)
    number_plus_count = a.count(number + 1)
    
    number_count += max(number_minus_count, number_plus_count)
    
    return number_count

for number in number_set:
    current_score = calculate_score(number, a)
    if(current_score > max_score):
        max_score = current_score
        
print(max_score)