#include<bits/stdc++.h>

using namespace std;

#define pb push_back
const int maxi = 1e6+10;
vector<int> v[maxi];
string s;
int n;
long long a[maxi];
long long ans;
void read_data()
{
    freopen("pairs.in","r", stdin);
    cin>>n;

    for (int i=1;i<=2*n;i++)
        scanf("%lld",&a[i]);
    fclose(stdin);
}

void print_data()
{
    freopen("pairs.out","w", stdout);
    cout<<ans<<endl;
    fclose(stdout);
}

void solve()
{
   sort(a+1, a+2*n+1);

   for (int i=1;i<=2*n;i+=2)
    ans+=a[i+1] -a[i];

}

int main()
{
    read_data();
    solve();
    print_data();

}

// ko mi tebe uze Tamara,
//prodala si suze drugima
//nocima ja sanjam tvoje tragove
//kuda idu izgubljene devojke