#!/bin/python

import sys
from collections import defaultdict

n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
d = defaultdict(int)
for x in a:
    d[x] += 1
m = 0
for i in range(101):
    m = max(m, d[i] + d[i + 1])
print m