import java.util.*;
public class Main{
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Integer a[] = new Integer[N];
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a, Comparator.reverseOrder());
        
        int A = 0;
        int B = 0;
        for(int i=0; i<N; i+=2){
            A += a[i];
        }
        for(int i=1; i<N; i+=2){
            B += a[i];
        }
        System.out.println(A-B);
    }
} import java.util.*; util.* java public class Main{
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Integer a[] = new Integer[N];
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a, Comparator.reverseOrder());
        
        int A = 0;
        int B = 0;
        for(int i=0; i<N; i+=2){
            A += a[i];
        }
        for(int i=1; i<N; i+=2){
            B += a[i];
        }
        System.out.println(A-B);
    }
} Main public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Integer a[] = new Integer[N];
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a, Comparator.reverseOrder());
        
        int A = 0;
        int B = 0;
        for(int i=0; i<N; i+=2){
            A += a[i];
        }
        for(int i=1; i<N; i+=2){
            B += a[i];
        }
        System.out.println(A-B);
    } main {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Integer a[] = new Integer[N];
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a, Comparator.reverseOrder());
        
        int A = 0;
        int B = 0;
        for(int i=0; i<N; i+=2){
            A += a[i];
        }
        for(int i=1; i<N; i+=2){
            B += a[i];
        }
        System.out.println(A-B);
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc Integer a[] = new Integer[N]; a new Integer[N] N for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        } int i=0; int i=0; i 0 i<N i N i++ i++ i {
            a[i] = sc.nextInt();
        } {
            a[i] = sc.nextInt();
        } a[i] = sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc Arrays.sort(a, Comparator.reverseOrder()) Arrays.sort Arrays a Comparator.reverseOrder() Comparator.reverseOrder Comparator int A = 0; A 0 int B = 0; B 0 for(int i=0; i<N; i+=2){
            A += a[i];
        } int i=0; int i=0; i 0 i<N i N i+=2 i+=2 i 2 {
            A += a[i];
        } {
            A += a[i];
        } A += a[i] A a[i] a i for(int i=1; i<N; i+=2){
            B += a[i];
        } int i=1; int i=1; i 1 i<N i N i+=2 i+=2 i 2 {
            B += a[i];
        } {
            B += a[i];
        } B += a[i] B a[i] a i System.out.println(A-B) System.out.println System.out System System.out A-B A B String[]args args public class Main{
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Integer a[] = new Integer[N];
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a, Comparator.reverseOrder());
        
        int A = 0;
        int B = 0;
        for(int i=0; i<N; i+=2){
            A += a[i];
        }
        for(int i=1; i<N; i+=2){
            B += a[i];
        }
        System.out.println(A-B);
    }
} public class Main{
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Integer a[] = new Integer[N];
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a, Comparator.reverseOrder());
        
        int A = 0;
        int B = 0;
        for(int i=0; i<N; i+=2){
            A += a[i];
        }
        for(int i=1; i<N; i+=2){
            B += a[i];
        }
        System.out.println(A-B);
    }
} Main
import java.util.*;
public class Main{
    public static void main(String[]args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        Integer a[] = new Integer[N];
        for(int i=0; i<N; i++){
            a[i] = sc.nextInt();
        }
        Arrays.sort(a, Comparator.reverseOrder());
        
        int A = 0;
        int B = 0;
        for(int i=0; i<N; i+=2){
            A += a[i];
        }
        for(int i=1; i<N; i+=2){
            B += a[i];
        }
        System.out.println(A-B);
    }
}
