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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		// 配列を準備
		// int[] array = new int[N];
		// 最初からリスト
		List<Integer> list = new ArrayList<>();
		// for文でN回繰り返し
		for (int i = 0; i < N; i++) {
			list.add(sc.nextInt());
		}
		Collections.sort(list);
		//Collections.reverse(list);
		//本当に反対にする必要があるか？
		// 大きい方から小さい方に？ 小さい方から大きい方に？⇒後で。

		// for(int i = 0; i < list.size();i++) {
		// 配列に対する操作であって、Collectionsに合わせたループがある
		boolean flag = true;
		int AliceMaxCount = 0;
		int BobMaxCount = 0;
		Iterator<Integer> i = list.iterator();
		while (i.hasNext()) {
			if (flag) {
				// true なので Alice
				// 該当カードを取得する
				AliceMaxCount += i.next();
				//
				flag = false;
			} else {
				// Bob
				BobMaxCount += i.next();
				flag = true;
			}
		}
		System.out.println(Math.abs(AliceMaxCount - BobMaxCount));
		sc.close();
	}
}