#!/bin/python

import sys


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

a.sort()
result = []
for i in range(len(a)):
    j = i
    while j < len(a) and abs(a[i] - a[j]) <= 1:
        j += 1
    result.append(j-i)
print max(result)