#!/bin/python

import sys


n = int(raw_input().strip())
a = sorted(map(int,raw_input().strip().split(' ')))
mp=2
mc=0
mn=0
for i in xrange(n):
    if i!=0:
        if a[i-1]<a[i]:
            if mp<mc:
                mp=mc
            mc = mn
            mn = 0
        if a[i]-a[i-1]<=1:
            mc+=1
            mn+=1
        else:
            if mp<mc:
                mp=mc
            mc = mn+1
            mn = 1
    else:
        mc+=1
        mn+=1
print max(mp,mc,mn)