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