import java.util.*;

public class Main {
    public static void main(String[] args) {
    	Scanner sc = new Scanner(System.in);
    	int N = Integer.parseInt(sc.next());
    	Integer a[] = new Integer[N];

    	for (int i=0; i<N; i++){
    		a[i] = Integer.parseInt(sc.next());
    	}

    	Arrays.sort(a, Collections.reverseOrder());

    	int ans = 0;

    	for(int i=0; i<N; i++){
    		if (i%2==0){
    			ans += a[i];
    		}else{
    			ans -= a[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