#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
d = [0]*101
for x in a:
    d[x] += 1
m = 0
for i in xrange(100):
    t = d[i]+d[i+1]
    if t>m:
        m = t
print m