#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
a.sort()
cnt=0
ans=0
for i in range(n):
    for j in range(i+1,n):
        if(a[j]-a[i]<=1):
            cnt+=1
        else:
            ans=max(ans,cnt)
            cnt=0
            break
    ans=max(ans,cnt) 
    cnt=0
print(ans+1 if n!=2 else '2')