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: Time Limit Exceeded)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace A
{
    class Program
    {
        static void Main(string[] args)
        {
            ABC132C();

            Console.ReadKey();
        }

        private static void ABC132C()
        {
            var n = long.Parse(Console.ReadLine());

            var d = Console.ReadLine().Split().Select(x => long.Parse(x)).ToArray();

            var max = d.Max();
            var min = d.Min();
            var c = 0;

            var lower = 0;
            var upper = 0;

            for (long j = min; j <= max; j++)
            {
                lower = 0;
                upper = 0;
                for (long i = 0; i < n; i++)
                {

                    if (d[i] <= j)
                    {
                        lower++;
                    }
                    else if (j + 1 <= d[i])
                    {
                        upper++;
                    }
                }

                if (lower == upper)
                {
                    c++;
                }
            }

            Console.WriteLine(c);
        }
    }
}