1092B.cpp

#include <bits/stdc++.h>
using namespace std;

int main() {
    ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
    int n;
    cin >> n;
    int arr[n];
    for (int i = 0; i < n; i++)
        cin >> arr[i];

    sort(arr, arr+n);
    int sel = 0;

    for (int i = 1; i < n; i += 2)
        sel += arr[i] - arr[i-1];
    
    printf("%d\n", sel);
}