Problem:
Score : 300 points

Problem Statement

You are given an integer sequence of length N, a_1,a_2,...,a_N.

For each 1≤i≤N, you have three choices: add 1 to a_i, subtract 1 from a_i or do nothing.

After these operations, you select an integer X and count the number of i such that a_i=X.

Maximize this count by making optimal choices.

Constraints

1≤N≤10^5

0≤a_i<10^5 (1≤i≤N)

a_i is an integer.

Input

The input is given from Standard Input in the following format:

N
a_1 a_2 .. a_N

Output

Print the maximum possible number of i such that a_i=X.

Sample Input 1

7
3 1 4 1 5 9 2

Sample Output 1

4

For example, turn the sequence into 2,2,3,2,6,9,2 and select X=2 to obtain 4, the maximum possible count.

Sample Input 2

10
0 1 2 3 4 5 6 7 8 9

Sample Output 2

3

Sample Input 3

1
99999

Sample Output 3

1

Solution in Python (3.4.3) (judge verdict: Runtime Error)

import collections
import math
import re
import numpy


def ai():return input()#s
def a():return int(input())#a,n or k
def ma():return map(int, input().split())#a,b,c,d or n,k
def ms():return map(str, input().split())#,a,b,c,d
def lma():return list(map(int, input().split()))#x or y
def lms():return list(map(str, input().split()))#x or y
k= []
l = []
f = 0
s=0
c=0
e =1
def say(i):return print("Yes" if i == 0 else "No")
def Say(i):return print("YES" if i == 0 else "NO")
#def rep(i):return for i in range()
a = a()
x = lma()
l = set(x)
m=1
for i in l:
    if i- tn==1:
        ta = tb
        tb = tc
        tc = x.count(i+1)
    else:
        ta = x.count(i-1)
        tb = x.count(i)
        tc = x.count(i+1)
    t = ta+tb+tc
    m=max(m,t)
    tn = i
print(m)