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 (7.3.0) (judge verdict: Wrong Answer)

N = int(input())
A = list(map(int, input().split()))
A.sort()
ans = 0
now = A[0]
start_idx = 0
while now <= A[-1] + 1:
    tmp_max = 0
    flag = True
    for i in range(start_idx, N):
        if flag and now - 1 == A[i]:
            flag = False
            start_idx = i
        if now - 1 <= A[i] <= now + 1:
            tmp_max += 1
        else:
            break
    ans = max(tmp_max, ans)
    now += 1
print(ans)