#!/bin/python3

import sys


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

longestRun=0
thisRun=0
a = sorted(a)
for i in range(n):
    thisRun=1
    for j in range(i+1,n):
        if a[j]-a[i]<=1:
            thisRun+=1
    if thisRun>longestRun:
        longestRun=thisRun
        
print(longestRun)