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


public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N;
		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 sum = 0;

		for(int i = 0; i < N; ++i) {
			if(i%2 == 0) sum += a[i];
			else sum -= a[i];
		}
		System.out.println(sum);
	}
} import java.util.Arrays; Arrays java.util import java.util.Comparator; Comparator 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;
		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 sum = 0;

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

		for(int i = 0; i < N; ++i) {
			if(i%2 == 0) sum += a[i];
			else sum -= a[i];
		}
		System.out.println(sum);
	} main {
		Scanner sc = new Scanner(System.in);
		int N;
		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 sum = 0;

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

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

		for(int i = 0; i < N; ++i) {
			if(i%2 == 0) sum += a[i];
			else sum -= a[i];
		}
		System.out.println(sum);
	}
} Main
import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;


public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N;
		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 sum = 0;

		for(int i = 0; i < N; ++i) {
			if(i%2 == 0) sum += a[i];
			else sum -= a[i];
		}
		System.out.println(sum);
	}
}
