Problem:
Score : 300 points

Problem Statement

Takahashi made N problems for competitive programming.
The problems are numbered 1 to N, and the difficulty of Problem i is represented as an integer d_i (the higher, the harder).

He is dividing the problems into two categories by choosing an integer K, as follows:

A problem with difficulty K or higher will be for ARCs.

A problem with difficulty lower than K will be for ABCs.

How many choices of the integer K make the number of problems for ARCs and the number of problems for ABCs the same?

Problem Statement

2 \leq N \leq 10^5

N is an even number.

1 \leq d_i \leq 10^5

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
d_1 d_2 ... d_N

Output

Print the number of choices of the integer K that make the number of problems for ARCs and the number of problems for ABCs the same.

Sample Input 1

6
9 1 4 4 6 7

Sample Output 1

2

If we choose K=5 or 6, Problem 1, 5, and 6 will be for ARCs, Problem 2, 3, and 4 will be for ABCs, and the objective is achieved.
Thus, the answer is 2.

Sample Input 2

8
9 1 14 5 5 4 4 14

Sample Output 2

0

There may be no choice of the integer K that make the number of problems for ARCs and the number of problems for ABCs the same.

Sample Input 3

14
99592 10342 29105 78532 83018 11639 92015 77204 30914 21912 34519 80835 100000 1

Sample Output 3

42685

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

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

namespace Atcoder
{
    class Program
    {
        static void Main(string[] args)
        {


			//テンプレート
			//// 整数の入力
			//int a = int.Parse(Console.ReadLine());
			//// スペース区切りの整数の入力
			//string[] input = Console.ReadLine().Split(' ');
			//int b = int.Parse(input[0]);
			//int c = int.Parse(input[1]);
			//// 文字列の入力
			//string s = Console.ReadLine();
			////出力
			//Console.WriteLine(a + b + c + " " + s);

			int a = int.Parse(Console.ReadLine());
			string[] input = Console.ReadLine().Split(' ');
			int[] d = new int[a];

			for (int i = 0;i < a;i++)
			{
				d[i] = int.Parse(input[i]);
			}

			Array.Sort(d);

			int min_point = 0;
			int max_point = 0;

			//for(int i= 0;i < a; i++)
			//{
			//	if (i >= d.Length /2 )
			//	{
			//		if(min_point != 0)
			//			min_point = i;

			//		if ((d.Length / 2 + 1) >= i)
			//		{
			//			max_point = i;
			//			break;
			//		}



			//	}
			//}

			Console.WriteLine(d[a/2] - d[a/2 - 1]);
			Console.ReadLine();

        }
    }
}