import java.util.*;
import java.math.*;
public class Main {
	public static void main(String[] args){
		
		Scanner sc = new Scanner(System.in);
		int K = sc.nextInt();
		int sum = 0;
		
        List<Integer> a = new ArrayList<>();
        for (int i = 0; i < K; i++) {
            int d = sc.nextInt();
			a.add(d);
		}
		Collections.sort(a,Collections.reverseOrder());	
		
		for(int i=0; i<a.size();i++)
		{
			sum += (Math.pow((-1),(i)))*(a.get(i));
		}
		System.out.println(sum);
   
        }
		
	}
/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