UVa 442 Matrix Chain Multiplication(矩陣鍊,模拟棧)

意甲冠軍  由于矩陣乘法計算連結清單達的數量，需要的計算  後的電流等于行的矩陣的矩陣的列數  他們乘足夠的人才  非法輸出error

輸入是嚴格合法的  即使僅僅有兩個相乘也會用括号括起來  并且括号中最多有兩個 那麼就非常easy了 遇到字母直接入棧  遇到反括号計算後入棧  然後就得到結果了

Suppose you have to evaluate an expression like A*B*C*D*E where A,B,C,D and E are matrices. Since matrix multiplication is associative, the order in which multiplications are performed is arbitrary. However, the number of elementary multiplications needed strongly depends on the evaluation order you choose.

For example, let A be a 50*10 matrix, B a 10*20 matrix and C a 20*5 matrix. There are two different strategies to compute A*B*C, namely (A*B)*C and A*(B*C).

The first one takes 15000 elementary multiplications, but the second one only 3500.

Your job is to write a program that determines the number of elementary multiplications needed for a given evaluation strategy.

Input consists of two parts: a list of matrices and a list of expressions.

The first line of the input file contains one integer n ( 

 ), representing the number of matrices in the first part. The next n lines each contain one capital letter, specifying the name of the matrix, and two integers, specifying the number of rows and columns of the matrix.

The second part of the input file strictly adheres to the following syntax (given in EBNF):

For each expression found in the second part of the input file, print one line containing the word "error" if evaluation of the expression leads to an error due to non-matching matrices. Otherwise print one line containing the number of elementary multiplications needed to evaluate the expression in the way specified by the parentheses.

10000

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