Given a balanced parentheses string?S, compute the score of the string based on the following rule:

• ()?has score 1
• AB?has score?A + B, where A and B are balanced parentheses strings.
• (A)?has score?2 * A, where A is a balanced parentheses string.

Example 1:

Input: "()"
Output: 1

Example 2:

Input: "(())"
Output: 2

Example 3:

Input: "()()"
Output: 2

Example 4:

Input: "(()(()))"
Output: 6

Note:

1. S?is a balanced parentheses string, containing only?(?and?).
2. 2 <= S.length <= 50

參考資料：

https://leetcode.com/problems/score-of-parentheses/

[LeetCode] Score of Parentheses 括號的分數