#!/bin/python
import sys
n = int(raw_input().strip())
a = map(int,raw_input().strip().split(' '))

a = sorted(a)
count = 0
count_old = 0
for i in range(len(a)):
    for j in range(i,len(a)):
        if a[j]-a[i] < 2:
            count+=1
        else:
            break
    if count_old < count:
        count_old = count
    count = 0
print count_old