#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a[100]={},ans=0;
	cin>>n;
	for(int i=0;i<n;i++)
		cin>>a[i];
	n+=n%2;
	sort(a,a+n);
	for(int i=0;i<n;i+=2)
		ans+=a[i+1]-a[i];
	cout<<ans<<endl;
}
