#!/bin/python

import sys


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

out = []
for i in xrange(101):
    out.append(0)
for x in a:
    out[x] += 1
mx = 0
for i in xrange(100):
    new = out[i] + out[i+1]
    mx = max(mx, new)
print mx