#include <bits/stdc++.h>
using namespace std;
int n, a[105], ans;

int main() {
	cin >> n;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	sort(a + 1, a + n + 1);
	for (int i = 1; i <= n; i += 2) {
		ans += a[i + 1] - a[i];
	}
	cout << ans;
	return 0;
}