#!/bin/python

import sys


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

uniqueNums = sorted(list(set(a)))

if len(uniqueNums) == 1:
    print len(a)
else:
    bestSoFar = 0
    for i,n in enumerate(uniqueNums):
        sumCt = a.count(n)
    
        if i != 0 and (n - uniqueNums[i-1]) < 2:
            sumCt += a.count(uniqueNums[i-1])
    
    
        if sumCt > bestSoFar:
            bestSoFar = sumCt

    print bestSoFar