import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

public class Solution {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] calories = new int[n];
        int sum=0;
        for(int i=0; i < n; i++){
            calories[i] = in.nextInt();
            sum=sum+calories[i]*(2^i);
        }
        System.out.println(sum);
        
        // your code goes here
    }
}