#include <iostream>
#include <fstream>
#include <algorithm>

using namespace std;
long long nums[200000];
int main()
{
    int N;
    ifstream fin("pairs.in");

    fin >> N;
    if (N < 1 || N > 100000)
    {
        cout << "Invalid N";
        return 1;
    }

    for (int i = 0; i < 2 * N; i++)
        fin >> nums[i];

    sort(nums, nums + 2 * N);
    long long total = 0;

    for (int i = 0; i < 2 * N; i += 2)
    {
        total += abs(nums[i] - nums[i + 1]);
    }

    ofstream fout("pairs.out");
    fout << total;
    return 0;
}