import java.util.*;
public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		List<Integer> cards = new ArrayList<Integer>();
		for(int i = 0;i < n ;i++) {
			cards.add(sc.nextInt());
		}
		Collections.sort(cards);
		Collections.reverse(cards);
		int ans = 0;
		for(int i = 0;i < n;i++) {
			if(i % 2 == 0) ans += cards.get(i);
			else ans -= cards.get(i);
		}
		System.out.println(ans);
        sc.close();
	}
}
/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