#!/bin/python

import sys


n = int(raw_input().strip())
a = sorted(map(int,raw_input().strip().split(' ')))
counts=[]
for i in range(n-1):
    j=i+1
    v=1
    while j<n and abs(a[i]-a[j])<=1:
        v+=1
        j+=1
    counts.append(v)
print max(counts)