#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
new_a=sorted(list(set(a)))
maxi=-1
store=[]
for x in range(len(new_a)-1):
    if (a.count(new_a[x+1])+a.count(new_a[x])) > maxi and abs((new_a[x+1])-(new_a[x]))<=1:
        maxi=(a.count(new_a[x+1]) + a.count(new_a[x]))
    store.append(a.count(new_a[x]))
    
store.append(a.count(new_a[len(new_a)-1]))  

if len(store)!=0:print(max(maxi,max(store)))
else:print(maxi)