#include<iostream>
#include<cstdio>
#include<queue>
using namespace std;
long long i,j,p,n,m,k;
priority_queue <long long> q;
int main()
{
    freopen("pairs.in", "r", stdin);
    freopen("pairs.out", "w", stdout);
    cin>>n;
    for(i=1;i<=2*n;i++)
    {
        scanf("%lld",&p);
        q.push(p);
    }
    while(!q.empty())
    {
        p=q.top();
        q.pop();
        n=q.top();
        q.pop();
        k+=p-n;
    }
    cout<<k;
    return 0;
}