Starting with the uppercase string s, repeatedly delete any adjacent AB or CD. The characters on either side join together after a deletion, which may allow more deletions. Return the shortest length you can obtain, including zero if everything can be removed.
Example 1:
Input: s = "A"
Output: 1Explanation: A single "A" contains neither "AB" nor "CD", so it cannot be removed.
Example 2:
Input: s = "B"
Output: 1Explanation: A single "B" contains neither removable pair, so its length stays 1.
Example 3:
Input: s = "AB"
Output: 0Explanation: Remove the pair "AB" in one operation. The remaining string is empty.
Constraints:
1 <= s.length <= 100- Only uppercase English letters occur.