New Year Book Reading

小明非常喜欢读书。他一共有 $n$ 本书，编号为 $1\sim n$，第 $i$本书重 $w_i$。 小明计划在暑假的 $m$ 天里每天读一本书，第 $i$ 天读第 $d_i$ 本书，可能会重复读到同一本书。 因为所有的书都是堆成一摞的，所以每次读某本书之前小明都需要先将这本书上面所有的书搬开，拿出这本书，再将搬开的书按原顺序放回去，消耗体力为搬开书的重量之和，读完这本书后将其放在这摞书的最上面。 小明想知道这 $n$ 本书以怎样的初始顺序放置，所搬书消耗总体力最小。 ### 输入格式 第一行两个正整数 $n,m$，表示小明一共有 $n$ 本书，要读 $m$ 天。 第二行 $n$ 个正整数，第 $i$ 个数表示表示第 $i$本书的重量为 $w_i$。 第三行 $m$ 个正整数，第 $i$ 个数表示第 $i$ 天要读第 $d_i$ 本书。 ### 输出格式 一行一个数，表示读完 $m$ 次书所搬书消耗的最小体力值。

New Year is coming, and Jaehyun decided to read many books during 2015, unlike this year. He has $ n $ books numbered by integers from 1 to $ n $ . The weight of the $ i $ -th ( $ 1<=i<=n $ ) book is $ w_{i} $ . As Jaehyun's house is not large enough to have a bookshelf, he keeps the $ n $ books by stacking them vertically. When he wants to read a certain book $ x $ , he follows the steps described below. 1. He lifts all the books above book $ x $ . 2. He pushes book $ x $ out of the stack. 3. He puts down the lifted books without changing their order. 4. After reading book $ x $ , he puts book $ x $ on the top of the stack.  He decided to read books for $ m $ days. In the $ j $ -th ( $ 1<=j<=m $ ) day, he will read the book that is numbered with integer $ b_{j} $ ( $ 1<=b_{j}<=n $ ). To read the book, he has to use the process described in the paragraph above. It is possible that he decides to re-read the same book several times. After making this plan, he realized that the total weight of books he should lift during $ m $ days would be too heavy. So, he decided to change the order of the stacked books before the New Year comes, and minimize the total weight. You may assume that books can be stacked in any possible order. Note that book that he is going to read on certain step isn't considered as lifted on that step. Can you help him?

The first line contains two space-separated integers $ n $ ( $ 2<=n<=500 $ ) and $ m $ ( $ 1<=m<=1000 $ ) — the number of books, and the number of days for which Jaehyun would read books. The second line contains $ n $ space-separated integers $ w_{1},w_{2},...,w_{n} $ ( $ 1<=w_{i}<=100 $ ) — the weight of each book. The third line contains $ m $ space separated integers $ b_{1},b_{2},...,b_{m} $ ( $ 1<=b_{j}<=n $ ) — the order of books that he would read. Note that he can read the same book more than once.

Print the minimum total weight of books he should lift, which can be achieved by rearranging the order of stacked books.

3 5
1 2 3
1 3 2 3 1

12

Here's a picture depicting the example. Each vertical column presents the stacked books.