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;

class Progaram
{
    static void Main(string[] args)
    {
        var n = Int32.Parse(Console.ReadLine());
        var l = Console.ReadLine().Split(' ').Select(x => Int32.Parse(x)).OrderByDescending(x => x).ToArray();
        var nl = new Int32[l[0] + 1];
        for (var i = 0; n > i; i++)
        {
            nl[l[i]]++;
        }
        var re = 0;
        var s = 0;
        for (var i = 0; nl.Length - 2 > i; i++)
        {
            var f = nl[i] + nl[i + 1] + nl[i + 2];
            if (re < f)
            {
                re = f;
                s = i;
            }
        }
        Console.WriteLine(re);
    }
}