#!/bin/python

import sys


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

res = 0
for i in xrange(n):
    c = 1
    for j in xrange(i+1, n):
        if a[j] - a[i] <= 1:
            c += 1
    res = max(res, c)
    
print res