#!/bin/python

import sys


n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))
A=sorted(a)
arr=[]
N=1
S=A[0]
c=0
while N<n:
    if (A[N]-S)<=1:
        c+=1
        
    else:
        arr.append(c)
        S=A[N]
        c=0
    N+=1
if arr:
    print max(arr)+1
else:
    print n