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 PyPy3 (2.4.0) (judge verdict: Accepted)

from sys import stdin
from collections import Counter


if __name__ == "__main__":
    _in = [_.rstrip() for _ in stdin.readlines()]
    N = int(_in[0])  # type:int
    a_arr = list(map(int,_in[1].split(' ')))  # type:list(int)
    # vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
    count = Counter(a_arr)
    cnt = 0
    keys = sorted(count.keys())
    for key in keys:
        _ = count[key]
        try:
            _ += count[key+1]
        except:
            pass
        try:
            _ += count[key-1]
        except:
            pass
        cnt = max(cnt,_)
    # ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    print(cnt)