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

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner stdIn = new Scanner(System.in);
		int N = stdIn.nextInt();
		ArrayList<Integer> a = new ArrayList<Integer>();
		for(int i = 0; i < N; i ++) {
			a.add(stdIn.nextInt());
		}
		
		Collections.sort(a);
		
		int ans = 0;
		for(int i = a.size() - 1; 0 <= i; i --) {
			ans += a.get(i);
			if(0 <= i - 1) {
				i --;
				ans -= a.get(i);
			}
		}
		System.out.println(ans);
	}

}
/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