#include <bits/stdc++.h>

using namespace std;

int main(){
    int n,sum=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++)
        {
        sum+=calories[i]*pow(2,i);
    }
    cout<<sum;
    // your code goes here
    return 0;
}