#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>

int main(){
    int n;
    long int sum=0;
    scanf("%d",&n);
    int *calories = malloc(sizeof(int) * n);
    for(int calories_i = 0; calories_i < n; calories_i++){
       scanf("%d",&calories[calories_i]);
    }
    // your code goes here
    for (int calories_i=0; calories_i<n; calories_i++)
    { 
        sum=sum+(calories[calories_i]*(2^calories_i));
    }
    printf("%ld",sum);
    return 0;
}