SetInputWeight across 3 or more AnimationClipPlayable

I can see many examples of mixing two animation clips:

Code (CSharp):

1. private void Update()
2. {
3.         mixerPlayable.SetInputWeight(0, 1 - blendVal);
4.         mixerPlayable.SetInputWeight(1, blendVal);
5. }

But what do I do when I have 3 or more playables? How do I blend 3 or more weights (blendVal) and ensure they equal 1?

Code (CSharp):

1. private void Update()
2. {
3.         mixerPlayable.SetInputWeight(0, (?? What goes here));
4.         mixerPlayable.SetInputWeight(1, (?? What goes here));
5. mixerPlayable.SetInputWeight(2, (?? What goes here));
6. }