#!/bin/python3
import sys
n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
l=[0]*99
l1=[]
for i in a:
    l[i-1]+=1
for j in range(98):
    l1.append(l[j]+l[j+1])
print (max(l1))