And the Particular Order is what makes this question non-trivial, the correct set in the wrong order is a wrong anwser.

In eMail no ORDER BY Clause, so people may be getting it wrong - Also really stupid to use such typo freindly names: just use A, B, C if you...

Your function may be overloading the call stack on recursion. You might try passing an incremented variable on each call and if > 1000 (or some convenient #) to exit...