#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))

upper_dict = dict()
lower_dict = dict()

for a_number in a:

    if a_number in upper_dict:
        upper_dict[a_number] += 1
        lower_dict[a_number] += 1

    if a_number+1 in lower_dict:
        lower_dict[a_number+1] += 1

    if a_number-1 in upper_dict:
        upper_dict[a_number-1] += 1

    if a_number not in upper_dict:
        upper_dict[a_number] = 1
    if a_number not in lower_dict:
        lower_dict[a_number] =1




ans = -1
for a_key in lower_dict:
    if lower_dict[a_key] > ans:
        ans = lower_dict[a_key]

for a_key in upper_dict:
    if upper_dict[a_key] > ans:
        ans = upper_dict[a_key]

print ans