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: Accepted)

import numpy as np
import collections
n=int(input())
a=list(map(int,input().split()))

#print(a[0])

b=np.zeros(n,dtype=int)
c=np.zeros(n,dtype=int)

for i in range(n):
    b[i]=a[i]-1
    c[i]=a[i]+1
#print(b)
#print(c)

mylist=[]
mylist.extend(a)
mylist.extend(b)
mylist.extend(c)

#print(mylist)

d=collections.Counter(mylist)
#print(d.most_common())
print(d.most_common()[0][1])