#include <bits/stdc++.h>

using namespace std;

int main(){
    int n;
    long int miles;
        miles=0;
    cin >> n;
    vector<int> calories(n);
    for(int calories_i = 0; calories_i < n; calories_i++){
       cin >> calories[calories_i];
    }
    for(int i=0;i<n;i++)
{
        miles=miles+(calories[i]*(2^i));
    }
    cout<<miles;    

}