#!/bin/python

import sys

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

maxi = 1
for i in range(0,n):
    curmax = 0
    for j in range(0, n):
        if a[i] - a[j] == 0 or (a[i] - a[j]) == 1:
            curmax+=1
    if curmax > maxi:
        maxi = curmax
print maxi