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)

from sys import stdin
import bisect

n = int(stdin.readline().rstrip())
li = list(map(int,stdin.readline().rstrip().split()))

li.sort()

ma = 0

if len(li) == 1:
    print(1)
elif len(li) == 2:
    if abs(li[0] - li[1]) <= 1:
        print(2)
    else:
        print(1)
else:
    for i in range(1,n-1):
        ma = max(ma,bisect.bisect(li,i+1)-bisect.bisect_left(li,i-1))

    print(ma)