#!/bin/python3

import sys
from collections import Counter
n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
c = Counter(a)
if len(c) == 1:
    print (n)
else:
    m = []
    for k in c:
        m.append(c[k])
        if k-1 in c:
            m.append(c[k] + c[k-1])
        if k+1 in c:
            m.append(c[k] + c[k+1])
    print (max(m))