CF1084A.The Fair Nut and Elevator

The Fair Nut lives in $n$ story house. $a_i$ people live on the $i$-th floor of the house. Every person uses elevator twice a day: to get from the floor where he/she lives to the ground (first) floor and to get from the first floor to the floor where he/she lives, when he/she comes back home in the evening.

It was decided that elevator, when it is not used, will stay on the $x$-th floor, but $x$ hasn't been chosen yet. When a person needs to get from floor $a$ to floor $b$, elevator follows the simple algorithm:

• Moves from the $x$-th floor (initially it stays on the $x$-th floor) to the $a$-th and takes the passenger.
• Moves from the $a$-th floor to the $b$-th floor and lets out the passenger (if $a$ equals $b$, elevator just opens and closes the doors, but still comes to the floor from the $x$-th floor).
• Moves from the $b$-th floor back to the $x$-th.

The elevator never transposes more than one person and always goes back to the floor $x$ before transposing a next passenger. The elevator spends one unit of electricity to move between neighboring floors. So moving from the $a$-th floor to the $b$-th floor requires $|a - b|$ units of electricity.

Your task is to help Nut to find the minimum number of electricity units, that it would be enough for one day, by choosing an optimal the $x$-th floor. Don't forget than elevator initially stays on the $x$-th floor.

公平坚果住在一栋 $n$ 层高的楼房中。第 $i$ 层住有 $a_i$ 人。每个人每天使用电梯两次：一次是从自己所住楼层前往地面（即第 1 层），另一次是在傍晚回家时从第 1 层前往自己所住楼层。

现决定：当电梯空闲时，将停靠在第 $x$ 层，但 $x$ 尚未选定。当某人需要从第 $a$ 层前往第 $b$ 层时，电梯按如下简单算法运行：

• 从第 $x$ 层（初始位置即为第 $x$ 层）出发，驶至第 $a$ 层接乘客；
• 从第 $a$ 层驶至第 $b$ 层并让乘客下车（若 $a = b$，电梯仅开关门，但仍需从第 $x$ 层驶至第 $a$ 层）；
• 从第 $b$ 层返回第 $x$ 层。

电梯每次最多运送一名乘客，且每次运送下一位乘客前，必定先返回第 $x$ 层。电梯在相邻楼层间移动消耗 1 单位电能，因此从第 $a$ 层移动到第 $b$ 层需消耗 $|a - b|$ 单位电能。

你的任务是帮助坚果选择最优的第 $x$ 层，使得电梯一天内所需电能总量最小。注意：电梯初始即停靠在第 $x$ 层。

The first line contains one integer $n$ ($1 \leq n \leq 100$) — the number of floors.

The second line contains $n$ integers $a_1, a_2, \ldots, a_n$ ($0 \leq a_i \leq 100$) — the number of people on each floor.

第一行包含一个整数 $n$（$1 \leq n \leq 100$）—— 楼层数。

第二行包含 $n$ 个整数 $a_1, a_2, \ldots, a_n$（$0 \leq a_i \leq 100$）—— 每层楼的人数。

In a single line, print the answer to the problem — the minimum number of electricity units.

在一行中输出问题的答案——最少的电能单位数。

In the first example, the answer can be achieved by choosing the second floor as the $x$-th floor. Each person from the second floor (there are two of them) would spend $4$ units of electricity per day ($2$ to get down and $2$ to get up), and one person from the third would spend $8$ units of electricity per day ($4$ to get down and $4$ to get up). $4 \cdot 2 + 8 \cdot 1 = 16$.

In the second example, the answer can be achieved by choosing the first floor as the $x$-th floor.

在第一个例子中，选择第二层作为第 $x$ 层即可得到答案。第二层的每个人（共两人）每天消耗 $4$ 单位电能（下楼 $2$ 单位，上楼 $2$ 单位），第三层的一个人每天消耗 $8$ 单位电能（下楼 $4$ 单位，上楼 $4$ 单位）。总消耗为 $4 \cdot 2 + 8 \cdot 1 = 16$。

在第二个例子中，选择第一层作为第 $x$ 层即可得到答案。