import java.util.*;

public class Main {
    public static void main(String[] args) {
        int ans=0;
        int bool = 1;
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        LinkedList<Integer> nums = new LinkedList<>();
        for(int i=0;i<n;i++){
            nums.add(sc.nextInt());
        }
        nums.sort(Collections.reverseOrder());
        for (int num:nums){
            ans += num*bool;
            bool=(-bool);
        }
        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