#include 
#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
int main() {
    
    int n;
    cin >> n;
    
    vector sum_left(19, 0), sum_right(19, 0);
    for(int i = 1; i <= n; i++) {
        int broj;
        cin >> broj;
        int p = n / 2;
        int t = 0;
        while(p >= 1) {
            if(i <= p) {
                sum_left[t] += broj;
            }
            else {
                sum_right[t] += broj;
            }
            t++;
            p /= 2;
        }
    }
    long long sum = 0;
    for(int i = 0; i < log2(n); i++) {
        sum_right[i] -= sum;
        sum += sum_right[i];
    }
    long long result = 0;
    for(int i = 0; i < log2(n); i++) {
        result += sum_left[i] - sum_right[i];
    }
    cout << result << endl;
    
    return 0;
}