import java.util.*;

public class Main {

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		}
		Arrays.sort(arr);
		int a = 0;
		int b = 0;
		for (int i = n - 1; i >= 0; i -= 2) {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		}
		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();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		}
		Arrays.sort(arr);
		int a = 0;
		int b = 0;
		for (int i = n - 1; i >= 0; i -= 2) {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		}
		System.out.println(a - b);
	}
} Main public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		}
		Arrays.sort(arr);
		int a = 0;
		int b = 0;
		for (int i = n - 1; i >= 0; i -= 2) {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		}
		System.out.println(a - b);
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		}
		Arrays.sort(arr);
		int a = 0;
		int b = 0;
		for (int i = n - 1; i >= 0; i -= 2) {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		}
		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 int[] arr = new int[n]; arr new int[n] n for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			arr[i] = sc.nextInt();
		} {
			arr[i] = sc.nextInt();
		} arr[i] = sc.nextInt() arr[i] arr i sc.nextInt() sc.nextInt sc Arrays.sort(arr) Arrays.sort Arrays arr int a = 0; a 0 int b = 0; b 0 for (int i = n - 1; i >= 0; i -= 2) {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		} int i = n - 1; int i = n - 1; i n - 1 n 1 i >= 0 i 0 i -= 2 i -= 2 i 2 {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		} {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		} a += arr[i] a arr[i] arr i if (i > 0) {
				b += arr[i - 1];
			} i > 0 i 0 {
				b += arr[i - 1];
			} b += arr[i - 1] b arr[i - 1] arr i - 1 i 1 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();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		}
		Arrays.sort(arr);
		int a = 0;
		int b = 0;
		for (int i = n - 1; i >= 0; i -= 2) {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		}
		System.out.println(a - b);
	}
} public class Main {

	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		}
		Arrays.sort(arr);
		int a = 0;
		int b = 0;
		for (int i = n - 1; i >= 0; i -= 2) {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		}
		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();
		int[] arr = new int[n];
		for (int i = 0; i < n; i++) {
			arr[i] = sc.nextInt();
		}
		Arrays.sort(arr);
		int a = 0;
		int b = 0;
		for (int i = n - 1; i >= 0; i -= 2) {
			a += arr[i];
			if (i > 0) {
				b += arr[i - 1];
			}
		}
		System.out.println(a - b);
	}
}
