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 Rust (1.15.1) (judge verdict: Accepted)

pub mod contest {
    pub mod input {
        use std::io;
        use std::str::FromStr;
        use std::fmt::Debug;

        pub fn read_line<F>() -> F
        where F: FromStr, <F as FromStr>::Err: Debug {
            let mut input = String::new();
            io::stdin().read_line(&mut input).unwrap();
            input.trim().parse().unwrap()
        }

        pub fn read_words<F>() -> Vec<F>
        where F: FromStr, <F as FromStr>::Err: Debug {
            let mut input = String::new();
            io::stdin().read_line(&mut input).unwrap();
            input
                .split_whitespace()
                .map(|i| i.parse().unwrap())
                .collect()
        }

        pub fn read_matrix<F>(num_lines: usize) -> Vec<Vec<F>>
        where F: FromStr, <F as FromStr>::Err: Debug {
            (0..num_lines).map(|_| read_words()).collect()
        }

        // 所有権的な問題で SplitWhitespace を直接持てないので妥協
        // まあ、一行のデータの数なんてそんなに多くないだろうし
        pub struct WordsReader {
            words: Vec<String>,
            cur: usize,
        }

        impl WordsReader {
            pub fn new() -> Self {
                let mut input = String::new();
                io::stdin().read_line(&mut input).unwrap();
                WordsReader {
                    words: input.split_whitespace().map(|i| i.to_owned()).collect(),
                    cur: 0,
                }
            }

            pub fn next<F>(&mut self) -> F
            where F: FromStr, <F as FromStr>::Err: Debug {
                let v: F = self.words[self.cur].parse().unwrap();
                self.cur += 1;
                v
            }
        }
    }
}

fn main() {
    let n: usize = contest::input::read_line::<usize>();
    let mut d: Vec<i32> = contest::input::read_words();
    d.sort();
    let ans = d[(n / 2)] - d[(n / 2) - 1];
    println!("{}", ans);
}