#!/bin/python3

import sys


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

ac = {}
for i in a:
    if i not in ac:
        ac[i] = 1
    else:
        ac[i] += 1
res = 0
for i in ac:
    if i-1 in ac:
        res = max(res, ac[i] + ac[i-1])
    if i+1 in ac:
        res = max(res, ac[i] + ac[i+1])
    res = max(res, ac[i])

print(res)