# include <bits/stdc++.h>
using namespace std;
int n,m;
long long a[1000005],b[1000005];

int main()
{
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout.tie(NULL);
freopen ("pairs.in","r",stdin);  freopen ("pairs.out","w",stdout);
long long i,j;
cin>>n;
n*=2;
for(i=1;i<=n;i++)
    cin>>a[i];
sort(a+1,a+n+1);
long long sum = 0;
for(i=2;i<=n;i+=2)
    sum+=(a[i]-a[i-1]);
cout<<sum<<endl;


return 0;
}