#!/bin/python

import sys


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

a.sort()
max_count = 0
max_so_far = 0
for i in range(n):
    max_so_far = 1
    for j in range(i+1,n):
        if abs(a[i] - a[j]) <= 1:
            max_so_far +=1
    if max_count < max_so_far:
        max_count = max_so_far
        
print max_count