#include<iostream>
#include<cstdio>
#include<iomanip>
#include<cmath>
#include<algorithm>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<stack>
#include<queue>
using namespace std;
long long a[200001],n,ans;
int main(){
int i,j;
freopen("pairs.in","rt",stdin);
freopen("pairs.out","wt",stdout);
cin>>n;
for(i=1;i<=2*n;i++){
	scanf("%lld",&a[i]);
}
sort(a+1,a+2*n+1);
for(i=1;i<=2*n;i+=2){
	ans+=(a[i+1]-a[i]);
}
cout<<ans<<endl;
return 0;
}
/*
6 4 
1 2
1 3
2 4
2 5
3 6
5 1
4 6
5 3
4 5


8
0 1 10
0 2 13
2 5 27
2 3 5
2 4 8
3 6 4
3 7 1
5
3 4 5
1 0 7
1 5 4
1 7 4
0 3 7
*/