#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
a.sort()
i = 0
c = 0
for j in range(n):
    i = j
    temp = 0
    while i<n and abs(a[i]-a[j])<=1:
        i+=1
        temp+=1
    if c<temp:
        c=temp
print c