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)

#![allow(unused_imports)]

use std::cmp::{max, min, Ordering};
use std::collections::*;
use std::iter::once;
#[cfg(debug_assertions)]
include! {"./debug.rs"}

#[cfg(not(debug_assertions))]
macro_rules! debug {
    ($($arg:expr),*) => {};
}

macro_rules! read {
    ([$t:ident] ; $n:expr) =>
        ((0..$n).map(|_| read!([$t])).collect::<Vec<_>>());
    ([$t:ident]) =>
        (rl().split_whitespace().map(|w| read_type!(w, $t)).collect::<Vec<_>>());
    (_, [$t:ident] ; $n:expr) =>
        ((0..$n).map(|_| read!(_, [$t])).collect::<Vec<_>>());
    (_, [$t:ident]) =>
        (rl().split_whitespace().skip(1).map(|w| read_type!(w, $t)).collect::<Vec<_>>());
    ($($t:ident),+ ; $n:expr) =>
        ((0..$n).map(|_| read!($($t),+)).collect::<Vec<_>>());
    ($t:ident) => (read_type!(rl(), $t));
    ($($t:ident),*) => {{
        let buf = rl();
        let mut w = buf.split_whitespace();
        ($(read_type!(w.next().unwrap(), $t)),*)
    }};
}

macro_rules! read_type {
    ($s:expr, chars) => {
        $s.chars().collect::<Vec<char>>()
    };
    ($s:expr, usize1) => {
        read_type!($s, usize) - 1
    };
    ($s:expr, $t:ty) => {
        $s.parse::<$t>().unwrap()
    };
}

fn rl() -> String {
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).unwrap();
    buf.trim_right().to_owned()
}

trait IteratorExt: Iterator + Sized {
    fn vec(self) -> Vec<Self::Item> {
        self.collect()
    }
}

impl<T: Iterator> IteratorExt for T {}

////////////////////////////////////////////////////////////////////////////////

fn main() {
    let n = read!(usize);
    let mut d = read!([i64]);

    d.sort();
    debug!(d);

    let ans = d[n / 2] - d[n / 2 - 1];

    println!("{}", ans);
}