#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
int main() {
    ios_base::sync_with_stdio(false);
    int n;
    cin >> n;
    long long L = 0, R = 0;
    for(int i = 1; i <= n; i++) {
        int x;
        cin >> x;
        int rundi = n;
        while(rundi > 1) {
            if(i <= rundi / 2) {
                L += x;
            }
            else if(i > rundi / 2 and i <= rundi) {
                R += x;
            }
            rundi /= 2;
        }
    }
    cout << L - R << endl;
    return 0;
}