#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
l=[]
for x in a:
    t=a.count(x)
    maxi=0
    mini=0
    if x+1 in a:
        r=a.count(x+1)
        maxi=+r
    if x-1 in a:
        r=a.count(x-1)
        mini=+r
    #print x,maxi,mini
    t=t+max([maxi,mini])
    l.append(t)
            
    
   
    
#print l            
print max(l)