import java.io.*;
public class Main{
    public static void main(String[] args) throws IOException{
        Reader r = new Reader();      
        int N = r.i();
        int[] a = r.ii();
        java.util.Arrays.sort(a);
        int sign = 1;
        int sum = 0;
        for(int i = 0; i < a.length; i++){
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        }        
        println(sum);
    }
    static void print(Object o){
        System.out.print(o.toString());
    }
    static void println(Object o){
        System.out.println(o.toString());
    }
    static class Reader extends BufferedReader{
        Reader(){
            super(new InputStreamReader(System.in));
        }
        String s() throws IOException{
            return readLine();
        }
        String[] ss() throws IOException{
            return s().split(" ");
        }
        int Int(String s){
            return Integer.parseInt(s);
        }
        int i() throws IOException{
            return Int(s());
        }
        int[] ii() throws IOException{
            String[] ss = ss();
            int size = ss.length;
            int[] ii = new int[size];
            for(int j = 0; j < size; j++) ii[j] = Int(ss[j]);
            return ii;
        }
    }
} import java.io.*; io.* java public class Main{
    public static void main(String[] args) throws IOException{
        Reader r = new Reader();      
        int N = r.i();
        int[] a = r.ii();
        java.util.Arrays.sort(a);
        int sign = 1;
        int sum = 0;
        for(int i = 0; i < a.length; i++){
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        }        
        println(sum);
    }
    static void print(Object o){
        System.out.print(o.toString());
    }
    static void println(Object o){
        System.out.println(o.toString());
    }
    static class Reader extends BufferedReader{
        Reader(){
            super(new InputStreamReader(System.in));
        }
        String s() throws IOException{
            return readLine();
        }
        String[] ss() throws IOException{
            return s().split(" ");
        }
        int Int(String s){
            return Integer.parseInt(s);
        }
        int i() throws IOException{
            return Int(s());
        }
        int[] ii() throws IOException{
            String[] ss = ss();
            int size = ss.length;
            int[] ii = new int[size];
            for(int j = 0; j < size; j++) ii[j] = Int(ss[j]);
            return ii;
        }
    }
} Main public static void main(String[] args) throws IOException{
        Reader r = new Reader();      
        int N = r.i();
        int[] a = r.ii();
        java.util.Arrays.sort(a);
        int sign = 1;
        int sum = 0;
        for(int i = 0; i < a.length; i++){
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        }        
        println(sum);
    } main {
        Reader r = new Reader();      
        int N = r.i();
        int[] a = r.ii();
        java.util.Arrays.sort(a);
        int sign = 1;
        int sum = 0;
        for(int i = 0; i < a.length; i++){
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        }        
        println(sum);
    } Reader r = new Reader(); r new Reader() int N = r.i(); N r.i() r.i r int[] a = r.ii(); a r.ii() r.ii r java.util.Arrays.sort(a) java.util.Arrays.sort java.util.Arrays java.util java java.util java.util.Arrays a int sign = 1; sign 1 int sum = 0; sum 0 for(int i = 0; i < a.length; i++){
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        } int i = 0; int i = 0; i 0 i < a.length i a.length a a.length i++ i++ i {
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        } {
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        } sum += a[a.length-1-i]*sign sum a[a.length-1-i]*sign a[a.length-1-i] a a.length-1-i a.length-1-i a.length a a.length 1 i sign sign = -sign sign -sign sign println(sum) println sum String[] args args static void print(Object o){
        System.out.print(o.toString());
    } print {
        System.out.print(o.toString());
    } System.out.print(o.toString()) System.out.print System.out System System.out o.toString() o.toString o Object o o static void println(Object o){
        System.out.println(o.toString());
    } println {
        System.out.println(o.toString());
    } System.out.println(o.toString()) System.out.println System.out System System.out o.toString() o.toString o Object o o static class Reader extends BufferedReader{
        Reader(){
            super(new InputStreamReader(System.in));
        }
        String s() throws IOException{
            return readLine();
        }
        String[] ss() throws IOException{
            return s().split(" ");
        }
        int Int(String s){
            return Integer.parseInt(s);
        }
        int i() throws IOException{
            return Int(s());
        }
        int[] ii() throws IOException{
            String[] ss = ss();
            int size = ss.length;
            int[] ii = new int[size];
            for(int j = 0; j < size; j++) ii[j] = Int(ss[j]);
            return ii;
        }
    } Reader Reader(){
            super(new InputStreamReader(System.in));
        } Reader {
            super(new InputStreamReader(System.in));
        } super(new InputStreamReader(System.in)) super new InputStreamReader(System.in) String s() throws IOException{
            return readLine();
        } s {
            return readLine();
        } return readLine(); readLine() readLine String[] ss() throws IOException{
            return s().split(" ");
        } ss {
            return s().split(" ");
        } return s().split(" "); s().split(" ") s().split s() s " " int Int(String s){
            return Integer.parseInt(s);
        } Int {
            return Integer.parseInt(s);
        } return Integer.parseInt(s); Integer.parseInt(s) Integer.parseInt Integer s String s s int i() throws IOException{
            return Int(s());
        } i {
            return Int(s());
        } return Int(s()); Int(s()) Int s() s int[] ii() throws IOException{
            String[] ss = ss();
            int size = ss.length;
            int[] ii = new int[size];
            for(int j = 0; j < size; j++) ii[j] = Int(ss[j]);
            return ii;
        } ii {
            String[] ss = ss();
            int size = ss.length;
            int[] ii = new int[size];
            for(int j = 0; j < size; j++) ii[j] = Int(ss[j]);
            return ii;
        } String[] ss = ss(); ss ss() ss int size = ss.length; size ss.length ss ss.length int[] ii = new int[size]; ii new int[size] size for(int j = 0; j < size; j++) ii[j] = Int(ss[j]); int j = 0; int j = 0; j 0 j < size j size j++ j++ j ii[j] = Int(ss[j]); ii[j] = Int(ss[j]) ii[j] ii j Int(ss[j]) Int ss[j] ss j return ii; ii BufferedReader public class Main{
    public static void main(String[] args) throws IOException{
        Reader r = new Reader();      
        int N = r.i();
        int[] a = r.ii();
        java.util.Arrays.sort(a);
        int sign = 1;
        int sum = 0;
        for(int i = 0; i < a.length; i++){
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        }        
        println(sum);
    }
    static void print(Object o){
        System.out.print(o.toString());
    }
    static void println(Object o){
        System.out.println(o.toString());
    }
    static class Reader extends BufferedReader{
        Reader(){
            super(new InputStreamReader(System.in));
        }
        String s() throws IOException{
            return readLine();
        }
        String[] ss() throws IOException{
            return s().split(" ");
        }
        int Int(String s){
            return Integer.parseInt(s);
        }
        int i() throws IOException{
            return Int(s());
        }
        int[] ii() throws IOException{
            String[] ss = ss();
            int size = ss.length;
            int[] ii = new int[size];
            for(int j = 0; j < size; j++) ii[j] = Int(ss[j]);
            return ii;
        }
    }
} public class Main{
    public static void main(String[] args) throws IOException{
        Reader r = new Reader();      
        int N = r.i();
        int[] a = r.ii();
        java.util.Arrays.sort(a);
        int sign = 1;
        int sum = 0;
        for(int i = 0; i < a.length; i++){
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        }        
        println(sum);
    }
    static void print(Object o){
        System.out.print(o.toString());
    }
    static void println(Object o){
        System.out.println(o.toString());
    }
    static class Reader extends BufferedReader{
        Reader(){
            super(new InputStreamReader(System.in));
        }
        String s() throws IOException{
            return readLine();
        }
        String[] ss() throws IOException{
            return s().split(" ");
        }
        int Int(String s){
            return Integer.parseInt(s);
        }
        int i() throws IOException{
            return Int(s());
        }
        int[] ii() throws IOException{
            String[] ss = ss();
            int size = ss.length;
            int[] ii = new int[size];
            for(int j = 0; j < size; j++) ii[j] = Int(ss[j]);
            return ii;
        }
    }
} Main
import java.io.*;
public class Main{
    public static void main(String[] args) throws IOException{
        Reader r = new Reader();      
        int N = r.i();
        int[] a = r.ii();
        java.util.Arrays.sort(a);
        int sign = 1;
        int sum = 0;
        for(int i = 0; i < a.length; i++){
            sum += a[a.length-1-i]*sign;
            sign = -sign;
        }        
        println(sum);
    }
    static void print(Object o){
        System.out.print(o.toString());
    }
    static void println(Object o){
        System.out.println(o.toString());
    }
    static class Reader extends BufferedReader{
        Reader(){
            super(new InputStreamReader(System.in));
        }
        String s() throws IOException{
            return readLine();
        }
        String[] ss() throws IOException{
            return s().split(" ");
        }
        int Int(String s){
            return Integer.parseInt(s);
        }
        int i() throws IOException{
            return Int(s());
        }
        int[] ii() throws IOException{
            String[] ss = ss();
            int size = ss.length;
            int[] ii = new int[size];
            for(int j = 0; j < size; j++) ii[j] = Int(ss[j]);
            return ii;
        }
    }
}