#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
i = 0
d = [0]
while(i<n):
    j = 0
    c = []
    count = 0
    
    while j<n:
        if(abs(a[i]-a[j])<=1):
           c.append(a[j])
        j = j + 1
    c.sort()
    x = abs(c[0]-c[len(c)-1])
    while(x>1):
            
            del c[len(c)-1]
            x = abs(c[0]-c[len(c)-1])
    d.append(len(c))                 
    i = i + 1
print max(d)