#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
low=min(a)
up=max(a)
lis=[]
for i in range(low,up+1):
    lis.append(a.count(i))
maa=0
if(up==low):
    maa=lis[0]
for i in range(0,up-low):
    if(lis[i]+lis[i+1]>maa):
        maa=lis[i]+lis[i+1]
print(maa)