#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
# put all of them into a hashtable/dictionary
dict = {}
for i in a:
    if (dict.has_key(i) == False):
        dict[i] = 1
    else:
        dict[i] = dict[i] + 1
L = dict.keys()
max = 0
if (len(L) == 1):
    if (dict[L[0]] > max):
        max = dict[L[0]]
for j in range(len(L)-1):
    if (dict[L[j]] > max):
        max = dict[L[j]]
    
    if (abs(L[j] - L[j+1]) <= 1 and dict[L[j]] + dict[L[j+1]] > max):
        max = dict[L[j]] + dict[L[j+1]]
print max