#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
result=0
temp=[0]*100
for x in a:
    temp[x-1]+=1
    temp[x]+=1
    pass
result=0
for x in temp:
    if x>result:
        result=x
        pass
    pass
print result