#include <bits/stdc++.h> using namespace std; int main(){ int n; cin>>n; int arr[n+1]; for (int i = 0;i<n;i++) cin>>arr[i]; sort(arr,arr+n,greater<int>()); arr[n] = 0; int g1 = arr[0],g2 = 0; for (int i = 3;i<n;i+=4){ g1 += (arr[i] + arr[i+1]); } for (int i = 1;i<n;i+=4){ g2 += (arr[i] + arr[i+1]); } cout<<abs(g2-g1)<<endl; return 0; }