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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
class Program
{
	static void Main()
	{
	int a = int.Parse(Console.ReadLine());//int.Parseは文字列を整数に変換。
	int[] nums = Array.ConvertAll(Console.ReadLine().Split(' '),int.Parse);
	int count = 0;
    int maxCount = 0;
      
      
      for(int i = 0; i < a; i++)
      {
        count = 0;
        for(int k = -1; k <= 1; k++)
        {
          if(i+k >= 0 && i+k < a)
          {
          if(nums[i+k] == nums[i])count ++;
          }
        }
        if(count > maxCount)maxCount = count;
      }
      
      Console.WriteLine(maxCount);
      
	}
}