using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
class Solution {

    static void Main(String[] args) {
        int n = Convert.ToInt32(Console.ReadLine());
        string[] calories_temp = Console.ReadLine().Split(' ');
        int[] calories = Array.ConvertAll(calories_temp,Int32.Parse);
        // your code goes here
        
        long milesToWalk = 0;
        for(int i = 0; i < n; i++) {
            milesToWalk += calories[i] * (2 ^ i);
        }
        Console.Write(milesToWalk.ToString());
    }
}