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.IO;
using System.Collections.Generic;

namespace _132
{
    class Program
    {
        static void Main(string[] args)
        {
            solve_132C();
        }


        public static void solve_132C()
        {
            int n = Convert.ToInt32(Console.ReadLine());
            string[] test = Console.ReadLine().Split(' ');

            int[] p = Array.ConvertAll(test, int.Parse);
            Array.Sort(p);

            int midL = p.Length / 2 - 1;

            int midR = p.Length / 2;

            int k = p[midR] - p[midL];
            Console.WriteLine(k);
        }

        public static void solve_132B()
        {
            int n = Convert.ToInt32(Console.ReadLine());
            string[] test = Console.ReadLine().Split(' ');

            int[] p = Array.ConvertAll(test, int.Parse);
            int count = 0;
            for (int i = 1; i < n; i++)
            {
                if (i < n - 1 && ((p[i] > p[i - 1] && p[i] < p[i + 1]) || (p[i] > p[i + 1] && p[i] < p[i - 1])))
                {
                    count++;
                }
            }

            Console.WriteLine(count);
        }
        public static void solve_132A()
        {
            string a = Console.ReadLine();

            char[] str = a.ToCharArray();

            Array.Sort(str);
            
            string ansewr = "Yes";
            if (str[0] != str[1] || str[2] != str[3] || str[0] == str[2])
            {
                ansewr = "No";
            }

            Console.WriteLine(ansewr);
        }
    }
}