New Year Book Reading

题意翻译

【题目描述】 小明非常喜欢读书，他有一共有n本书，编号为1~n，第i本书重wi。小明计划在暑假的m天里每天读一本书，第i天读第di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wi。 第三行m个正整数，第i个数表示第i天要读第di本书。 【输出格式】 仅一行一个数，表示读完m次书所搬书消耗的最小体力值。

题目描述

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?

输入输出格式

输入格式

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.

输出格式

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

输入输出样例

输入样例 #1

3 5
1 2 3
1 3 2 3 1

输出样例 #1

12

说明

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