#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))

c = dict()
for i in a:
    if i in c:
        c[i] += 1
    else:
        c[i] = 1

max_val = max(c.values())

keys = c.keys()
keys = sorted(keys)

s = 0

while s < len(keys):
    t = s
    tmp = 0
    while t < len(keys) and abs(keys[t] - keys[s]) <= 1:
        tmp += c[keys[t]]
        t += 1
    if tmp > max_val:
        max_val = tmp
    s += 1

print max_val