#!/bin/python

import sys


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

a = sorted(a)
c = 0
temp = 0
for i in range(len(a)):
   for j in range(i, len(a)):
       if a[j]-a[i] < 2:
           c += 1
       else:
           break
            
   if temp < c:
       temp = c
   c = 0
print temp