#!/bin/python3

import sys


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

count = {}
for nb in a:
    if nb in count:
        count[nb] += 1
    else:
        count[nb] = 1

map_lst = list(count.keys())
sorted(map_lst)
max_nb = 0

for i in range(len(map_lst) - 1):
    first = map_lst[i]
    second = map_lst[i + 1]
    
    if second - first <= 1 and count[first] + count[second] > max_nb:
        max_nb = count[map_lst[i]] + count[map_lst[i + 1]]
    elif count[first] > max_nb:
        max_nb = count[first]

last = map_lst[len(map_lst) - 1]
if count[last] > max_nb:
    max_nb = count[last]

print(max_nb)