import java.util.Arrays;
import java.util.Collections;
import java.util.Scanner;

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, Collections.reverseOrder());
		
		int dif = 0;
		for(int i = 0;i < a.length;i++) {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		}

		System.out.println(dif);
    }
} import java.util.Arrays; Arrays java.util import java.util.Collections; Collections java.util import java.util.Scanner; Scanner 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, Collections.reverseOrder());
		
		int dif = 0;
		for(int i = 0;i < a.length;i++) {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		}

		System.out.println(dif);
    }
} 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, Collections.reverseOrder());
		
		int dif = 0;
		for(int i = 0;i < a.length;i++) {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		}

		System.out.println(dif);
    } 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, Collections.reverseOrder());
		
		int dif = 0;
		for(int i = 0;i < a.length;i++) {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		}

		System.out.println(dif);
    } 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] a i sc.nextInt() sc.nextInt sc Arrays.sort(a, Collections.reverseOrder()) Arrays.sort Arrays a Collections.reverseOrder() Collections.reverseOrder Collections int dif = 0; dif 0 for(int i = 0;i < a.length;i++) {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		} int i = 0; int i = 0; i 0 i < a.length i a.length a a.length i++ i++ i {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		} {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		} if(i % 2 == 0) dif += a[i];
		    else dif -= a[i]; i % 2 == 0 i % 2 i 2 0 dif += a[i] dif a[i] a i dif -= a[i] dif a[i] a i System.out.println(dif) System.out.println System.out System System.out dif 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, Collections.reverseOrder());
		
		int dif = 0;
		for(int i = 0;i < a.length;i++) {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		}

		System.out.println(dif);
    }
} 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, Collections.reverseOrder());
		
		int dif = 0;
		for(int i = 0;i < a.length;i++) {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		}

		System.out.println(dif);
    }
} Main
import java.util.Arrays;
import java.util.Collections;
import java.util.Scanner;

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, Collections.reverseOrder());
		
		int dif = 0;
		for(int i = 0;i < a.length;i++) {
		    if(i % 2 == 0) dif += a[i];
		    else dif -= a[i];
		}

		System.out.println(dif);
    }
}