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) {
        int miles=0;
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] calories = new int[n];
        for(int i=0; i < n; i++){
            calories[i] = in.nextInt();
        }
        for(int j=0;j<n;j++)
        {
            miles+=calories[j]*(2^j);
            }// your code goes here
        System.out.println(miles);
    }
}