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 Kotlin (1.0.0) (judge verdict: Accepted)

fun main(array: Array<String>) {
    val n = readLine()?.toInt() ?: return
    val d = readLine()?.split(" ")?.map(String::toInt) ?: return
    val count = hashMapOf<Int, Int>()
    d.sorted().forEachIndexed { i, v ->
        if (!count.containsKey(v)) {
            count[v] = i + 1
        } else {
            count[v] = count[v]!! + 1
        }
    }
    val m = n / 2
    var l = -1
    count.keys.sorted().forEachIndexed { i, v ->
        if (l != -1) {
            println((v - l).toString())
            return
        } else if (count[v] == m) {
            l = v
        }
    }
    println("0")
}