import java.util.Arrays;
import java.util.Collections;
import java.util.Scanner;

public class Main {
    public static void main(String args[]) throws Exception {
        Scanner s = new Scanner(System.in);
        int n = s.nextInt();
        Integer l[] = new Integer[n];
        for (int i = 0; i < l.length; i++) {
            l[i] = s.nextInt();
        }
        Arrays.sort(l, Collections.reverseOrder());
        int sum = 0;
        for (int i = 0; i < l.length; i++) {
            if (i % 2 == 0) {
                sum = sum + l[i];
            } else {
                sum = sum - l[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