Problem:
Score: 200 points

Problem Statement

We have N cards. A number a_i is written on the i-th card.

Alice and Bob will play a game using these cards. In this game, Alice and Bob alternately take one card. Alice goes first.

The game ends when all the cards are taken by the two players, and the score of each player is the sum of the numbers written on the cards he/she has taken. When both players take the optimal strategy to maximize their scores, find Alice's score minus Bob's score.

Constraints

N is an integer between 1 and 100 (inclusive).

a_i \ (1 \leq i \leq N) is an integer between 1 and 100 (inclusive).

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 a_3 ... a_N

Output

Print Alice's score minus Bob's score when both players take the optimal strategy to maximize their scores.

Sample Input 1

2
3 1

Sample Output 1

2

First, Alice will take the card with 3. Then, Bob will take the card with 1.
The difference of their scores will be 3 - 1 = 2.

Sample Input 2

3
2 7 4

Sample Output 2

5

First, Alice will take the card with 7. Then, Bob will take the card with 4. Lastly, Alice will take the card with 2. The difference of their scores will be 7 - 4 + 2 = 5. The difference of their scores will be 3 - 1 = 2.

Sample Input 3

4
20 18 2 18

Sample Output 3

18

Solution in Rust (1.42.0) (judge verdict: Accepted)

struct Read<R: std::io::BufRead> {
    stdin: R,
    v: Vec<String>,
    i: usize,
}
impl<R:std::io::BufRead> Read<R> {
    pub fn new(stdin: R) -> Self {
        Read{
            stdin: stdin,
            v: Vec::new(),
            i: 0,
        }
    }
    pub fn read_line(&mut self) {
        self.i = 0; self.v.clear();
        let mut buf = String::new();
        self.stdin.read_line(&mut buf).unwrap();
        let buf = buf.trim().to_owned();
        let mut ws = buf.split_whitespace();
        loop {
            let x = ws.next();
            if x.is_none() {break;}
            let x = x.unwrap().to_owned();
            self.v.push(x);
        }
    }
    #[allow(dead_code)]
    pub fn read_t<T: std::str::FromStr>(&mut self) -> T {
        if self.i == self.v.len() {self.read_line();}
        let elem = &self.v[self.i];
        self.i += 1;
        elem.parse().unwrap_or_else(|_| panic!())
    }
    
    #[allow(dead_code)]
    pub fn read_i32(&mut self) -> i32 {
        if self.i == self.v.len() {self.read_line();}
        let elem = self.v[self.i].parse().unwrap();
        self.i += 1;
        elem
    }
    #[allow(dead_code)]
    pub fn read_usize(&mut self) -> usize {
        if self.i == self.v.len() {self.read_line();}
        let elem = self.v[self.i].parse().unwrap();
        self.i += 1;
        elem
    }
    #[allow(dead_code)]
    pub fn read_u64(&mut self) -> u64 {
        if self.i == self.v.len() {self.read_line();}
        let elem = self.v[self.i].parse().unwrap();
        self.i += 1;
        elem
    }
    #[allow(dead_code)]
    pub fn read_string(&mut self) -> String {
        if self.i == self.v.len() {self.read_line();}
        let elem = &self.v[self.i];
        self.i += 1;
        elem.to_owned()
    }
}
fn main() {
    use std::io;
    let stdin = io::stdin();
    let stdin = io::BufReader::new(stdin.lock());
    let read = Read::new(stdin);
    solve(read);
}

fn solve<R: std::io::BufRead>(mut r: Read<R>) {
    let n = r.read_usize();
    let mut a:Vec<i32> = Vec::new();
    for i in 0..n {
        a.push(r.read_i32());
    }
    a.sort();
    let mut suma = 0;
    let mut sumb = 0;
    for i in (0..n).into_iter().step_by(2) {
        suma+=a[i];
    }
    for i in (1..n).into_iter().step_by(2) {
        sumb+=a[i];
    }
    println!("{}",(suma-sumb).abs())
}