import java.util.Scanner;
import java.util.ArrayList;
import java.util.Collections;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		ArrayList<Integer> list = new ArrayList<>();
		int N = sc.nextInt();
		int result = 0;

		while (sc.hasNextInt()) {
			list.add(sc.nextInt());
		}
		Collections.sort(list, Collections.reverseOrder());
		
		int sign = 1;
		for (int tmp : list) {
			result += tmp * sign;
			sign *= -1;
		}
		
		System.out.println(result);
	}
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz