#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 runda = n;
        while(runda > 1) {
            if(i <= (runda / 2)) {
                L += x;
            }
            else if(i > (runda / 2) and i <= runda){
                R += x;
            }
            runda /= 2;
        }
        
    }
    cout << L - R << endl;
     return 0;
}