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

public class GFG
{
    static public void Main()
    {
        try
        {
            // var n = Console.ReadLine();
            //var input1 = Console.ReadLine().Split(' ');
            //var n = int.Parse(input1[0]);
            //var b = int.Parse(input1[1]);
            var n = int.Parse(Console.ReadLine());
            var aar = Console.ReadLine().Split(' ').Select(x => Int32.Parse(x)).ToArray();

            Together(n, aar);
        }
        catch (Exception ex)
        {
            Console.Write(ex);
        }
    }

    static void Together(int n, int[] arr)
    {
        Array.Sort(arr);
        int count = 1;
        arr[0] = arr[0] + 1;
        for (int i = 1; i < n; i++)
        {
            if (arr[i] - arr[i - 1] == -1)
            {
                arr[i] = arr[i] + 1;
            }
            else if (arr[i] - arr[i - 1] == 1)
            {
                arr[i] = arr[i] - 1;
                
            }

        }

        var ans = arr.GroupBy(x => x).Select(g => new { num = g.Key, count = g.Count() });
        int max = 0;
        foreach(var cc in ans)
        {
            if (cc.count > max)
                max = cc.count;
        }
        Console.Write(max);

    }
}