#!/bin/python

import sys


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

a.sort()
ans = 0
for i in xrange(n):
    for j in xrange(n):
        if abs(a[j] - a[i]) <= 1:
            ans = max(ans, j - i + 1)
print ans