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: Wrong Answer)

using System;
using System.IO;
using System.Linq;
class sol
{
    static StreamWriter sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
    static Scan sc = new Scan();

    static void Main(string[] args)
    {
        int n = sc.Int;
        var d = sc.IntArr;
        Array.Sort(d);
        foreach (int j in d)
        {
            Console.WriteLine(j);
        }
        int ans = 0;
        int i = d.Count<int>();
        Console.WriteLine(i);
        if(d[i/2-1] - d[i/2] == 0)
        {
            ans = 0;
        }
        else
        {
            ans = d[i/2] - d[i/2 - 1];
            Console.WriteLine(d[i / 2] + "," + d[i / 2 -1]);
        }
        Prt(ans);
        sw.Flush();
    }
    static void Prt(string a) => sw.WriteLine(a);
    static void Prt(params object[] a) => Prt(string.Join(" ", a));
}

class Scan
{
    StreamReader sr;
    public Scan() { sr = new StreamReader(Console.OpenStandardInput()); }
    public string Str => sr.ReadLine().Trim();
    public int Int => int.Parse(Str);
    public string[] StrArr => Str.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
    public int[] IntArr => StrArr.Select(int.Parse).ToArray();
    T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
    T cv<T>(string s) => ct<T, int>(int.Parse(s));
    public void Multi<T, U, V>(out T a, out U b, out V c)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); }
}