#!/bin/python3

import sys

n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]

dic = {}
for v in a:
    dic[v] = dic.get(v, 0) + 1
    dic[v+1] = dic.get(v+1, 0) + 1
print(max(dic.values()))