#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
counter=[0]*101

for x in a:
    counter[x]+=1
the_max=0
for i in xrange(100):
    the_num=counter[i]+counter[i+1]
    if the_num>the_max:
        the_max=the_num
print the_max