import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int sumA = 0, sumB = 0;
		int cnt = 0;
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			cnt++;
		}
		int tmp;
		for(int i = 0; i < n; i++) {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		}
		int i = 0;
		while(i < n - 1) {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		}
		if(cnt % 2 != 0) {
			sumA += a[n - 1];
		}
		System.out.println(sumA - sumB);
	}
} 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();
		int sumA = 0, sumB = 0;
		int cnt = 0;
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			cnt++;
		}
		int tmp;
		for(int i = 0; i < n; i++) {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		}
		int i = 0;
		while(i < n - 1) {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		}
		if(cnt % 2 != 0) {
			sumA += a[n - 1];
		}
		System.out.println(sumA - sumB);
	}
} Main public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int sumA = 0, sumB = 0;
		int cnt = 0;
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			cnt++;
		}
		int tmp;
		for(int i = 0; i < n; i++) {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		}
		int i = 0;
		while(i < n - 1) {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		}
		if(cnt % 2 != 0) {
			sumA += a[n - 1];
		}
		System.out.println(sumA - sumB);
	} main {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int sumA = 0, sumB = 0;
		int cnt = 0;
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			cnt++;
		}
		int tmp;
		for(int i = 0; i < n; i++) {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		}
		int i = 0;
		while(i < n - 1) {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		}
		if(cnt % 2 != 0) {
			sumA += a[n - 1];
		}
		System.out.println(sumA - sumB);
	} Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int n = sc.nextInt(); n sc.nextInt() sc.nextInt sc int sumA = 0 sumA 0 sumB = 0; sumB 0 int cnt = 0; cnt 0 int[] a = new int[n]; a new int[n] n for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			cnt++;
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			a[i] = sc.nextInt();
			cnt++;
		} {
			a[i] = sc.nextInt();
			cnt++;
		} a[i] = sc.nextInt() a[i] a i sc.nextInt() sc.nextInt sc cnt++ cnt int tmp; tmp for(int i = 0; i < n; i++) {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		} int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		} {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		} for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			} int k = i + 1; int k = i + 1; k i + 1 i 1 k < n k n k++ k++ k {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			} {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			} if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				} a[i] < a[k] a[i] a i a[k] a k {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				} tmp = a[i] tmp a[i] a i a[i] = a[k] a[i] a i a[k] a k a[k] = tmp a[k] a k tmp int i = 0; i 0 while(i < n - 1) {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		} i < n - 1 i n - 1 n 1 {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		} sumA += a[i] sumA a[i] a i sumB += a[i + 1] sumB a[i + 1] a i + 1 i 1 i += 2 i 2 if(cnt % 2 != 0) {
			sumA += a[n - 1];
		} cnt % 2 != 0 cnt % 2 cnt 2 0 {
			sumA += a[n - 1];
		} sumA += a[n - 1] sumA a[n - 1] a n - 1 n 1 System.out.println(sumA - sumB) System.out.println System.out System System.out sumA - sumB sumA sumB String[] args args public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int sumA = 0, sumB = 0;
		int cnt = 0;
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			cnt++;
		}
		int tmp;
		for(int i = 0; i < n; i++) {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		}
		int i = 0;
		while(i < n - 1) {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		}
		if(cnt % 2 != 0) {
			sumA += a[n - 1];
		}
		System.out.println(sumA - sumB);
	}
} public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int sumA = 0, sumB = 0;
		int cnt = 0;
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			cnt++;
		}
		int tmp;
		for(int i = 0; i < n; i++) {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		}
		int i = 0;
		while(i < n - 1) {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		}
		if(cnt % 2 != 0) {
			sumA += a[n - 1];
		}
		System.out.println(sumA - sumB);
	}
} Main
import java.util.Scanner;
public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int sumA = 0, sumB = 0;
		int cnt = 0;
		int[] a = new int[n];
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			cnt++;
		}
		int tmp;
		for(int i = 0; i < n; i++) {
			for(int k = i + 1; k < n; k++) {
				if(a[i] < a[k]) {
					tmp = a[i];
					a[i] = a[k];
					a[k] = tmp;
				}
			}
		}
		int i = 0;
		while(i < n - 1) {
			sumA += a[i];
			sumB += a[i + 1];
			i += 2;
		}
		if(cnt % 2 != 0) {
			sumA += a[n - 1];
		}
		System.out.println(sumA - sumB);
	}
}