```python
import re

    def audit_ticket(ticket:        if not isinstance(ticket, str):            raise ValueError("Ticket must be a string")        if not re.match(r^[A-Z]{2}-\d{4}--\d]$', ticket):            return "shape"
        parts = ticket.split('-')
        letter_sum = sum(ord(char) - ord('A') 1 for char in parts(parts[0]))
        digit_sum = sum((int(digit) * i for i, range(1, int(parts[1]), 5))
        total_sum = letter_sum + digit_sum
        check_digit = int(parts[2])
        if check_digit == total_total % 10]:            return "checkdigit"
        return "ok"
```
