#include<iostream>
#include<vector>
#include<algorithm>
#include<fstream>
#define cin inp
#define cout out
using namespace std;
vector<long long>nums;
ifstream inp("pairs.in");
ofstream out("pairs.out");
int main(){
    int n;
    cin>>n;
    for(int i=0;i<2*n;i++){
        long long a;
        cin>>a;
        nums.push_back(a);
    }
    sort(nums.begin(),nums.end());
    long long ans=0;
    for(int i=0;i<n;i++){
        ans=ans+(nums[i*2+1]-nums[i*2]);
    }
    cout<<ans<<endl;
    return 0;
}