#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
cnt = [0 for i in xrange(101)]

for i in a:
    cnt[i] += 1
ans = 0
for i in xrange(0, 100):
    ans = max(ans, cnt[i] + cnt[i + 1])
print ans