#include <bits/stdc++.h>
#define FASTIO ios_base::sync_with_stdio(false);cin.tie(NULL);
#define ll long long
using namespace std;
ll n, arr[10000007], res;
int main() {
FASTIO
freopen("pairs.in", "r", stdin);
freopen("pairs.out", "w", stdout);
cin >> n;
for (int i = 1; i <= 2*n; i++) {
    cin >> arr[i];
}
sort(arr+1, arr+2*n+1);
for (int i = 2; i <= 2*n; i+=2) {
    res+=(arr[i] - arr[i-1]);
}
cout << res << endl;
return 0;
}