#!/bin/python3

import sys


n = int(input().strip())
a = [int(a_temp) for a_temp in input().strip().split(' ')]
counts = {}
for i in a:
    if i not in counts:
        counts[i] = 1
    else:
        counts[i] += 1
curmax = None    
for k in counts:
    curcount = counts[k]
    leftcount = 0
    rightcount = 0
    if k-1 in counts:
        leftcount = counts[k-1]
    if k+1 in counts:
        rightcount = counts[k+1]
    thismax = curcount + max(leftcount, rightcount)
    if curmax == None or thismax > curmax:
        curmax = thismax
print(curmax)