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)

# encoding: "utf-8"

from numpy import array

class Stdin:
    @staticmethod
    def read_line(converter=str):
        return [converter(x) for x in input().split()]
    
    @staticmethod
    def read_lines(n, converter=str):
        result = list()
        for _ in range(n):
            result.append(Stdin.read_line(converter))
        return result
    
    @staticmethod
    def convert(data, converter):
        assert(len(data) == len(converter))
        return tuple(map(lambda x, f: f(x), data, converter))

    @staticmethod
    def convert_lines(datas, n, converter):
        return [converter(data, n, converter) for data in datas]


def main():
    _ = input()
    xs = Stdin.read_line(converter=int)
    ys = array(list(map(lambda x: [x-1, x, x+1], xs))).flatten()
    ys.sort()
    cnt = 0
    m = 0
    prev = ys[0]
    for y in ys:
        if y == prev:
            cnt += 1
        else:
            if m < cnt:
                m = cnt
            prev = y
            cnt = 1
    print(m)

if __name__ == "__main__":
    main()