#include<bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define ll long long
using namespace std;

ll n,lista[400000];

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);

    freopen("pairs.in","r",stdin);
    freopen("pairs.out","w",stdout);

    cin >> n;
    ll res=0;
    for(ll i=1;i<=2*n;i++){
        cin >> lista[i];
    }
    sort(lista+1,lista+1+2*n);
    for(ll i=1;i<=2*n;i+=2){
        res+=abs(lista[i]-lista[i+1]);
    }
    cout << res;
    return 0;
}