#!/bin/python3
import collections
import sys


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

for i in range(n):
    exist = numbers.get(a[i], None)
    if(exist == None):
        numbers[a[i]] = 1
    else:
        numbers[a[i]] += 1
number_list = list(numbers)
numbers = collections.OrderedDict(sorted(numbers.items()))
maks = 2

if(len(number_list) == 1):
    maks = numbers[number_list[0]]

for i in range(len(number_list) - 1):
    if abs(number_list[i] - number_list[i + 1]) <= 1:
        curr = numbers[number_list[i]] + numbers[number_list[i+1]]
        
        if(maks < curr):
            maks = curr

for x in numbers:
    if maks < numbers[x]:
        maks = numbers[x]
print(maks)