How can I prevent shadow sprite overlap?

I have sprite shadows that have been given to me by my artist and I like the way they look, however I would like them not to overlap as seen in the image. I want them to remain the same transparency regardless of how many are overlapping. This could be a little complicated, so I am also open to alternatives to get the same effect (such as shaders.) I have researched how to allow sprites to do this via shaders have had a rough time with it. Thank you for your time.