#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
a.sort()
maxi = 0

for i in xrange(n):
    prev = a[i]
    j = i
    count = 0
    while j<n and abs(a[i]-a[j])<2 :
        count+=1
        j+=1
    if count>maxi:
        maxi=count
print maxi