题解 | #HJ070 矩阵乘法计算量估算#

import java.util.*;

/**
 * HJ70 矩阵乘法计算量估算 - 中等
 */
public class HJ070 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNextLine()) {
            int n = Integer.parseInt(sc.nextLine());
            int[][] num = new int[n][2];
            for (int i = 0; i < n; i++) {
                String[] arr = sc.nextLine().split(" ");
                num[i][0] = Integer.parseInt(arr[0]);
                num[i][1] = Integer.parseInt(arr[1]);
            }
            String msg = sc.nextLine();
            Stack<Integer> z = new Stack<>();
            int count = 0;
            for (int j = 0; j < msg.length(); j++) {
                char tmp = msg.charAt(j);
                if (tmp != '(') {
                    if (tmp == ')') {
                        int cc = z.pop();
                        int cr = z.pop();
                        int bc = z.pop();
                        int br = z.pop();
                        count += br * cc * bc;
                        z.push(br);
                        z.push(cc);
                    } else {
                        int index = tmp - 'A';
                        z.push(num[index][0]);
                        z.push(num[index][1]);
                    }
                }
            }
            System.out.println(count);
        }
        sc.close();
    }
}