The error you’re getting isn’t helpful in your case (not your fault, whoever coded Donacode didn’t abstract away their errors). It’s attempting to convert a complex number to a floating point number somewhere under the hood.
I see one little mistake here that could the source to the problem (the text editor thinks this is a complex number and is trying to make sense of the value):
That’s the only thing I can see in your code that could be the issue 