A cash machine accepts a PIN only if it is made of digits only and is exactly 4 or 6 characters long. Given the string pin, return True if it is acceptable and False otherwise. Spaces, signs and decimal points are not digits.
Examples
Input: pin = "1234"
Output: True
Input: pin = "12345"
Output: False
Input: pin = "12a4"
Output: False
Constraints
0 <= len(pin) <= 20pinmay contain any printable characters
Goals
- Check the length of a string
- Check that every character is a digit
- Return a boolean