#include<bits/stdc++.h>
using namespace std;
priority_queue<int> q;
int main(){
	int n;
	cin>>n;
	for(int i=1;i<=n;i++){
		int y;
		cin>>y;
		q.push(y);
	}
	int cnt=0,cnt1=0;
	for(int i=1;i<=n;i++){
		if(i%2==1){
			cnt+=q.top();
			q.pop();
		}else{
			cnt1+=q.top();
			q.pop();
		}
	}
	cout<<cnt-cnt1;
	return 0;
}