#!/bin/python

import sys

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

max_result = 0 
A = sorted(A) 

for a in A: 
    left_count = A.count(a) + A.count(a-1) 
    right_count = A.count(a) + A.count(a+1) 
    count = max(left_count,right_count) 
    if max_result < count:
        #print "a:"+str(a)
        #print "count:"+str(count)
        max_result = count 

print max_result