#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
t=list(set(a))
t.sort()

maxi=0
for i in range(len(t)):
    temp=a.count(t[i])
    if t[i]+1 in t:
        temp=a.count(t[i])+a.count(t[i]+1)
    if temp>maxi:
        maxi=temp
            
print(maxi)