#!/bin/python

import sys
import collections


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

hist = collections.Counter(a)

distinct_values = sorted(hist.keys())
len_d = len(distinct_values)

prev_val = None
best = 0
temp = 0

for d in distinct_values:
    #print "d:", d
    #print "temp:", temp
    #print "best:", best
    #print "prev:", prev_val
    if prev_val is None:
        prev_val = d
        temp = hist[d]
    elif abs(d - prev_val) <= 1:
        temp += hist[d]
    if temp > best:
        best = temp
    temp = hist[d]
    prev_val = d

print best