#!/bin/python

import sys

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

#i-1<=j<=i+1

d={i:0 for i in list(set(a))}

for i in d:
    ctr1=0
    ctr2=0
    for j in xrange(n):
        if i-1==a[j] or a[j]==i:
            ctr1+=1
        if i-1==a[j] or a[j]==i:
            ctr2+=1
    d[i]=max(ctr1,ctr2)
    
print max(d.values())