#!/bin/python

import sys

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


b = []
for i in a:
    count1 = 0
    count2 = 0
    for j in a:
        if j == i + 1:
            count1 += 1
        elif j == i - 1:
            count2 += 1
        elif j == i:
            count1 += 1
            count2 += 1
    if count1 > count2:
        b.append(count1)
    else:
        b.append(count2)
print max(b)