#include <fstream>
#include <algorithm>

using namespace std;

int main()
{
	ifstream inpf("pairs.in", ios::in);
	int n;
	unsigned long long a[200000], diff = 0;
	inpf >> n;
	n <<= 1;
	for(int i = 0; i < n; ++i)
	{
		inpf >> a[i];
	}
	
	sort(a, a+n);
	for(int i = 0; i < n; i+=2)
	{
		diff += a[i+1] - a[i];
	}
	
	ofstream outf("pairs.out", ios::out);
	outf << diff << endl;
	
	return 0;
}