#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
leng=0
arr=sorted(a)
for i in range(n):
    count=0
    for j in range(i,n):
        if(abs(arr[i]-arr[j])<=1):
            count+=1
    if(count>leng):
        leng=count
print leng