Is That a Real Date?

Write is_valid_date(s) that returns True if s is a real calendar date written as YYYY-MM-DD:

• exactly 10 characters: four digits, -, two digits, -, two digits
• year between 0001 and 9999
• month between 01 and 12
• day between 01 and the number of days in that month; February has 29 days in a leap year (divisible by 4, except centuries unless divisible by 400)

Examples

Input:  s = "2024-02-29"
Output: True

Input:  s = "2023-02-29"
Output: False

Input:  s = "1999-12-31"
Output: True

Constraints

• 0 <= len(s) <= 20, printable ASCII
• Do not use the datetime module

Goals

• Check a fixed-width format position by position
• Convert validated digit groups to numbers
• Apply the leap-year rule to February