You're welcome, I glad the debugging went quickly ;)

I will close this issue therefore.

I have also edited the kata description (kata author isn't active) to explicity include examples of the kind of invalid inputs that may be encountered.

Hi - I don't use C# so I can't view your current solution to see what's going on; until another user checks your Issue here are some general suggestions though:

• Add a print/stdout statement so you can see which test inputs are causing which tests to fail, you can learn to do this here https://docs.codewars.com/training/troubleshooting/#error-messages-and-printing-your-inputoutput

• Invalid inputs are things with double digits e.g. [10,12,57] or negative numbers [-2,-5] etc; while you wait for someone to look at your code, check on your local machine if your current code produces an answer for the above 2 tests?

Please use spoiler flag next time.