题解 | #矩阵乘法计算量估算#

import java.util.*;
public class Main {
        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 == '(') {
                       continue;
                    } else 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);
            }
        }
}