#!/bin/python3

import sys


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

new_list = []
for i in range(n):
    dist = [a[i]]
    for index, aa in enumerate(a):
        if abs(aa - a[i]) <= 1 and index != i:
            all = True
            for j in range(len(dist)):
                if abs(dist[j] - aa) > 1:
                    all = False
            if all:
                dist.append(aa)
    new_list.append(dist)

print(max(list(map(lambda x:len(x), new_list))))