491. Alternating Case Score

Given a string s, calculate a score based on the case of its characters. The first character always adds 1 to the score. For each later character, add 2 if its case (uppercase vs lowercase) is different from the previous character, otherwise add 1. Non-alphabetic characters count as having no case and still add 1 point.

Example:
Input: s = "A B"
Output: 3

Explanation: 'A' adds 1. The space adds 1. 'B' is uppercase like the most recent alphabetic character, so it adds 1 more. The total score is 3.

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