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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

/*  
    Talkin' to myself and feelin' old
    Sometimes I'd like to quit, nothin' ever seems to fit
    Hangin' around, nothin' to do but frown
    Rainy days and Mondays always get me down
    _________________________
    _________________________
    960 Hours of Solitude
    Quarantine_Day : 40
*/

#include<bits/stdc++.h>

using namespace std;

typedef long long int       ll;
typedef vector<int>         vi;
typedef vector<ll>          vl;
typedef pair<int, int>      pii;
typedef pair<ll, ll>		pll;

#define pb(n)           push_back(n)
#define GSORT(v)        sort(v.begin(), v.end(), greater<ll>())
#define SORT(v)         sort(v.begin(), v.end());
#define REV(v)          reverse(v.begin(), v.end());
#define db(a)           cout<<#a<<" = "<<a<<endl;
#define FIN             freopen("in.txt","r",stdin);
#define FOUT            freopen("out.txt","w",stdout);
#define REP(i,n)        for(int i = (int)(0); i < (int)(n); i++)
#define FOR(i, a, b)    for(int i = (int)a; i <= (int)b; i++)    

#define MAX 200005

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);

    ll n; cin>>n;
    vl v(n);
    REP(i, n) cin>>v[i];
    GSORT(v);
    ll a(0), b(0);
    REP(i, n){
        if(i & 1) b += v[i];
        else a += v[i];
    }
    cout<<abs(a - b)<<"\n";

    return 0;
}