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: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace algorithm
{
	class Program
	{
		public static void Main()
		{
			Console.ReadLine();
			var tmp = Array.ConvertAll(Console.ReadLine().Split(), int.Parse);
			List<int> nm = tmp.ToList();
			int l = 0, r = 1;
			int v = 0;
			int max = 0;
			if (nm.Count==1)
			{
				max = 1;
			}
			else
			{
				nm.Sort();
				while (r < nm.Count)
				{
					if (nm[l] == nm[r] || nm[l] == nm[r] - 1 || nm[l] == nm[r] - 2)
					{
						r++;
						max = Math.Max(max, r - l);
					}
					else
					{
						l++;
						r = l;
					}
				}
			}


			Console.WriteLine(max);

		}
	}
}