#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]

max = 0
a = sorted(a)
#print(a)
for i in range(n-1):
    nbr = 1
    for j in range(i+1, n):
        if a[j]-a[i]<=1:
            nbr += 1
            #print("i={0}, j={1}, a[{0}]={2}, a[{1}]={3}, diff = {4}, nbr={5}".format(i,j,a[i],a[j],a[j]-a[i],nbr))
            
            if nbr > max:
                max = nbr
        else:
            if nbr > max:
                max = nbr
            break

print(max)