#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))

alreadyDone = set()
bestCount = 0
for i in a:
    count = 0
    if i in alreadyDone: continue
    s = []
    for val in a:
        if val <= i+1 and val >= i:
            count += 1
            s.append(val)
    if count > bestCount:
        bestCount = count
    
    alreadyDone.add(i)

alreadyDone = set()
for i in a:
    count = 0
    if i in alreadyDone: continue
    s = []
    for val in a:
        if val <= i and val >= i - 1:
            count += 1
            s.append(val)
    if count > bestCount:
        bestCount = count
    
    alreadyDone.add(i)
    
print bestCount