I guess the author should add a little more detail in the problem statement. I didn't fully understand what was required, especially the "edge consists of N balls" part. Or maybe I am bad at maths. :-)

I agree. But then I did this for Python, and saw all reference answers for Python as well.
I was more worried towards the complexity of the solution.
With respect, I guess the best answers are chosen on the amount of code written (smaller the better), even if they compromise on performance. Since I am new here, I will find out how much of this is true!

This is a great Kata.
I took so much time to finish this, trying to avoid nested loops.
But then the top answers are all nested loops! This looks weird.
Do we have any performance metrics to pass too?
Thanks anyway. :)