//include
//------------------------------------------
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <ctime>

using namespace std;

//int→string
//string→int
//------------------------------------------
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}

//sqrt
//-------------------------------------------
template<class T> inline T sqr(T x) {return x*x;}

//typedef
//------------------------------------------
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef long long LL;

//container util
//------------------------------------------
#define ALL(a)  (a).begin(),(a).end()
#define RALL(a) (a).rbegin(), (a).rend()
#define PB push_back
#define MP make_pair
#define SZ(a) int((a).size())
#define EACH(i,c) for(typeof((c).begin()) i=(c).begin(); i!=(c).end(); ++i)
#define EXIST(s,e) ((s).find(e)!=(s).end())
#define SORT(c) sort((c).begin(),(c).end())
#define RSORT(c) sort((c).rbegin(),(c).rend())

//repetition
//------------------------------------------
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n)  FOR(i,0,n)
#define REPR(i, n) for(int i = n;i >= 0;i--)

//constant
//--------------------------------------------
const double EPS = 1e-10;
const double PI  = acos(-1.0);

//clear memory
#define CLR(a) memset((a), 0 ,sizeof(a))

//debug
#define dump(x)  cerr << #x << " = " << (x) << endl;
#define debug(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ")" << " " << __FILE__ << endl;


//#define EPS (1e-10)
//
//struct Point{
//    Point(double _x = 0, double _y = 0){
//        x = _x;
//        y = _y;
//    }
//    double x;
//    double y;
//
//    Point operator + (Point p){
//        return Point(x + p.x, y+ p.y);
//    }
//
//    Point operator - (Point p){
//        return Point(x - p.x, y - p.y);
//    }
//
//    Point operator * (double a){
//        return Point(a * x, a * y);
//    }
//
//    Point operator / (double a){
//        return Point(x / a, y / a);
//    }
//
//    double abs(){
//        return sqrt(norm());
//    }
//
//    double norm(){
//        return x * x + y * y;
//    }
//
//    bool operator < (const Point &p) const{
//        return x!=p.x ? x < p.x : y < p.y;
//    }
//
//    bool operator == (const Point &p) const{
//        return fabs(x - p.x) && fabs(y - p.y) < EPS;
//    }
//
//};
//
//typedef Point Vector;
//
//double dot(Vector a, Vector b){
//    return a.x * b.x + a.y * b.y;
//}

int main() {

    int N; scanf("%d", &N);
    int alice = 0;
    int bob = 0;
    VI cards(N);
    REP(i, N){
        scanf("%d", &cards[i]);
    }
    RSORT(cards);

    for(int i=0;i<N; i+=2){
        alice += cards[i];
    }
    for(int i=1;i<N;i+=2){
        bob += cards[i];
    }

    printf("%d",alice- bob);


    return 0;

}

Measured memory_bytes: 256