#!/bin/python

import sys


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

a.sort()

maxCt = 1
ct = 0
st  = a[0]
for i in range(n):
    
    if a[i] - st <= 1:
        ct+=1
    else:
        ct=1
        st  = a[i]
    if ct > maxCt:
        maxCt = ct

        
print maxCt