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

class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] a = new int[N];
		for(int i = 0; i < N; i++) a[i] = sc.nextInt();
		Arrays.sort(a);
		int sum = 0;
		for(int i = 0; i < N; i++) {
			if(i % 2 == 0) sum += a[N - 1 - i];
			else sum -= a[N - 1 - i];
		}
		System.out.println(sum);
	}
} import java.util.Arrays; Arrays java.util import java.util.Scanner; Scanner java.util class Main{
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] a = new int[N];
		for(int i = 0; i < N; i++) a[i] = sc.nextInt();
		Arrays.sort(a);
		int sum = 0;
		for(int i = 0; i < N; i++) {
			if(i % 2 == 0) sum += a[N - 1 - i];
			else sum -= a[N - 1 - i];
		}
		System.out.println(sum);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] a = new int[N];
		for(int i = 0; i < N; i++) a[i] = sc.nextInt();
		Arrays.sort(a);
		int sum = 0;
		for(int i = 0; i < N; i++) {
			if(i % 2 == 0) sum += a[N - 1 - i];
			else sum -= a[N - 1 - i];
		}
		System.out.println(sum);
	} main {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int[] a = new int[N];
		for(int i = 0; i < N; i++) a[i] = sc.nextInt();
		Arrays.sort(a);
		int sum = 0;
		for(int i = 0; i < N; i++) {
			if(i % 2 == 0) sum += a[N - 1 - i];
			else sum -= a[N - 1 - i];
		}
		System.out.println(sum);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int N = sc.nextInt(); N sc.nextInt() sc.nextInt sc int[] a = new int[N]; a new int[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) Arrays.sort Arrays a int sum = 0; sum 0 for(int i = 0; i < N; i++) {
			if(i % 2 == 0) sum += a[N - 1 - i];
			else sum -= a[N - 1 - i];
		} int i = 0; int i = 0; i 0 i < N i N i++ i++ i {
			if(i % 2 == 0) sum += a[N - 1 - i];
			else sum -= a[N - 1 - i];
		} {
			if(i % 2 == 0) sum += a[N - 1 - i];
			else sum -= a[N - 1 - i];
		} if(i % 2 == 0) sum += a[N - 1 - i];
			else sum -= a[N - 1 - i]; i % 2 == 0 i % 2 i 2 0 sum += a[N - 1 - i] sum a[N - 1 - i] a N - 1 - i N - 1 - i N 1 i sum -= a[N - 1 - i] sum a[N - 1 - i] a N - 1 - i N - 1 - i N 1 i System.out.println(sum) System.out.println System.out System System.out sum String[] args args
import java.util.Arrays;
import java.util.Scanner;

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