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)

#include <bits/stdc++.h>
 
using namespace std;
 
#define xx         first
#define yy         second
#define pb         push_back
#define mp         make_pair
#define LL         long long
#define inf        INT_MAX/3
#define mod        1000000007ll
#define PI         acos(-1.0)
#define linf       (1ll<<60)-1
#define FOR(I,A,B) for(int I = (A); I < (B); ++I)
#define REP(I,N)   FOR(I,0,N)
#define For(I,N)   for(int I=1;I<=(N);I++)
#define ALL(A)     ((A).begin(), (A).end())
#define set0(ar)   memset(ar,0,sizeof ar)
#define vsort(v)   sort(v.begin(),v.end())
#define setinf(ar) memset(ar,126,sizeof ar)
#define SZ(X) ((int)(X.size()))
#define LG(X) ((int)(X.length()))
#define CL(X) (X).clear()
#define MAXEL(A,B) (*max_element(A,B))
#define MINEL(A,B) (*min_element(A,B))
#define ROPEN(X) freopen(X,"r",stdin)
#define WOPEN(X) freopen(X,"w",stdout)
#define BG(X) (X.begin())
#define EN(X) (X.end())
#define VI vector<int>
#define PII pair<int,int>
 
//cout << fixed << setprecision(20) << p << endl;
 
template <class T> inline T bigmod(T p,T e,T M){
    LL ret = 1;
    for(; e > 0; e >>= 1){
        if(e & 1) ret = (ret * p) % M;
        p = (p * p) % M;
    } return (T)ret;
}
template <class T> inline T gcd(T a,T b){if(b==0)return a;return gcd(b,a%b);}
template <class T> inline T modinverse(T a,T M){return bigmod(a,M-2,M);}


int main(){
	ios_base::sync_with_stdio(false);
    cin.tie(NULL);
	int n;
	cin>>n;
	int s=0;
	int arr[101];
	for(int i=0;i<n;i++){
		cin>>arr[i];
	}
	sort(arr,arr+n,greater<int>());
	for(int i=0;i<n;i++){
		if(i%2==0)s+=arr[i];
		if(i%2==1)s-=arr[i];
	}
	cout<<s<<endl;
	return 0
	;
}