#!/bin/python

import sys


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

maxSelected = 0

for i in range(max(ar)):
    ar_prime = filter(lambda x: x == i or x == i+1, ar)
    selected = len(ar_prime)
    maxSelected = max(maxSelected, selected)
    
print maxSelected