#!/bin/python3

import sys


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

d = [0] * 120

for i in a:
    d[i]+=1

ans = 0
for i in range(110):
    ans = max(ans, d[i] + d[i+1])
print(ans)