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 (2.7.6) (judge verdict: Accepted)

# vim: set fileencoding=utf-8:
from collections import Counter


def main():
    N = input()
    a = [int(ele) for ele in raw_input().split()]
    a_plus = [ele + 1 for ele in a]
    a_minus = [ele - 1 for ele in a]
    ct = Counter(a)
    ct_plus = Counter(a_plus)
    ct_minus = Counter(a_minus)

    for k, v in ct_plus.items():
        ct[k] += v

    for k, v in ct_minus.items():
        ct[k] += v

    print(ct.most_common()[0][1])


if __name__ == "__main__":
    main()