921 - Minimum Add to Make Parentheses Valid.

Medium

A parentheses string is valid if and only if:

• It is the empty string,

• It can be written as AB (A concatenated with B), where A and B are valid strings, or

• It can be written as (A), where A is a valid string.

You are given a parentheses string s. In one move, you can insert a parenthesis at any position of the string.

• For example, if s = "()))", you can insert an opening parenthesis to be <code>"( ( )))"</code> or a closing parenthesis to be <code>"()) ) )"</code>.

Return the minimum number of moves required to make s valid.

Example 1:

Input: s = "())"

Output: 1

Example 2:

Input: s = "((("

Output: 3

Constraints:

• 1 <= s.length <= 1000

• s[i] is either '(' or ')'.