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