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;
using static System.Console;
using static System.Math;

namespace C_ABC132
{
    class MainClass
    {

        static int[] s;
        static int[] n;

        public static void Main(string[] args)
        {
            n = Array.ConvertAll(ReadLine().Split().ToArray(), int.Parse);
            s = Array.ConvertAll(ReadLine().Split().ToArray(), int.Parse);
            var sl = s.ToList();
            sl.Sort();
            int mid = n[0] / 2;
            int ans = 0;
            if (n[0] % 2 == 1)
            {
                WriteLine(ans);
                return;
            }
            if (sl[mid] == sl[mid - 1])
            {
                WriteLine(ans);
                return;
            }
            else
            {
                ans = sl[mid] - sl[mid - 1];
                WriteLine(ans);
                return;
            }

        }
    }
}