#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
s = {}
for i in a:
    s[i] = s.get(i,0)+1
    s[i+1] = s.get(i+1,0)+1
c=max(s.values())
print(c)