#include <iostream>
#include <vector>
#include <algorithm>

int main() {
    int n;
    std::cin >> n;
    std::vector<int> data;
    for (int i = 0; i != n * 2; i++) {
        int temp;
        std::cin >> temp;
        data.push_back(temp);
    }
    std::sort(data.begin(), data.end());
    int double_place = n - 1;
    int one_place = 2;
    int diff = 0;
    for (int i = 1; i <= double_place * 2; i += 2) {
        diff += (data[i] - data[i - 1]);
    }
    std::cout << diff << std::endl;
    return 0;
}