#!/bin/python3

import sys

n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
newa = list(set(a))
c = []
for number in newa:
    if number + 1 in newa:
        count = a.count(number) + a.count(number+1)
        c.append(count)
    elif number -1 in newa:
        count = a.count(number) + a.count(number-1)
        c.append(count)
    else:
        c.append(a.count(number))
print(max(c))