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: Accepted)

using System;
using System.Linq;//リストの使用
using System.Collections.Generic;
using System.Text;//テキストの高速出力に必要
class Program
{
	static void Main()
	{
    long n = long.Parse(Console.ReadLine());
    long[] nums = Array.ConvertAll(Console.ReadLine().Split(' '),long.Parse);
		long[] answers = new long[100002];
    long answer = 0;
    for(int i = 0; i < n; i++)
    {
      answers[nums[i]]++;
      answers[nums[i]+1]++;
      answers[nums[i]+2]++;
    }
    for(int i = 0; i < 100002; i++)
    {
      answer = Math.Max(answer, answers[i]);
    }
		Console.WriteLine(answer);//WriteLineをWriteとすると、改行なしで出力。
	}
}