#include <bits/stdc++.h>
using namespace std;
const int inf = 0x3f3f3f3f, mod = 1000000007;
const long long INF = 0x3f3f3f3f3f3f3f3fLL;
const double pi = acosl(-1.), eps = 1e-9;
inline int power(int a, int b, int m = mod, int ans = 1) {
  for (; b; b >>= 1, a = 1LL * a * a % m)
    if (b & 1) ans = 1LL * ans * a % m;
  return ans;
}
int main() {
  int a[111];
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  int ans = 0;
  for (int i = 0; i < n; i += 2) ans += abs(a[i + 1] - a[i]);
  cout << ans << endl;
  return 0;
}
