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 (3.8.2) (judge verdict: Accepted)

n = int(input())
a = list(map(int, input().split()))

def func(a):
  count = [0] * (max(a)+1)

  for i in a:
      count[i] += 1

  max_n = 0
  for j in range(1, len(count)-1):
      max_n = max(max_n, count[j] + count[j-1] + count[j+1])
  max_n = max(max_n, count[-1] + count[-2])

  return max_n

print(n if len(set(a)) == 1 else func(a))