#include <iostream>
#include <algorithm>
#include <cstdio>
using namespace std;

int n;
long long a[200001],sum;

int main()
{
int i;
    freopen("pairs.in","rt",stdin);
     freopen("pairs.out","wt",stdout);
    scanf("%d", &n);
    for(i=1;i<=2*n;i++)scanf("%d", &a[i]);
    sort(a+1,a+2*n+1);
    for(i=1;i<2*n;i+=2){
        sum+=abs(a[i]-a[i+1]);
    }
    printf("%d", sum);

    return 0;
}