#!/bin/python
from collections import *
import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
cnt = Counter(a)
sum = 0
temp1 = 0
temp2 = 0
for x in set(a):
    temp1 = cnt[x+1] + cnt[x]
    temp2 = cnt[x] + cnt[x-1]
    sum = max(sum,temp1,temp2)
print sum