B - Card Game for Two

﻿配点：200

### 問題文

N 枚のカードがあります. i 枚目のカードには, a_i という数が書かれています.
Alice と Bob は, これらのカードを使ってゲームを行います. ゲームでは, Alice と Bob が交互に 1 枚ずつカードを取っていきます. Alice が先にカードを取ります.
2 人がすべてのカードを取ったときゲームは終了し, 取ったカードの数の合計がその人の得点になります. 2 人とも自分の得点を最大化するように最適な戦略を取った時, Alice は Bob より何点多く取るか求めてください.

### 制約

• N1 以上 100 以下の整数
• a_i \ (1 \leq i \leq N)1 以上 100 以下の整数

### 入力

N
a_1 a_2 a_3 ... a_N


### 入力例 1

2
3 1


### 出力例 1

2


### 入力例 2

3
2 7 4


### 出力例 2

5


### 入力例 3

4
20 18 2 18


### 出力例 3

18


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