Generating multiple R.java and combining them?

I am doing a custom build, but I am trying to integrate UnityAds. Unityads has its own resources and hence generates its own R.java resource classes with its own package. My game also uses native resources and generates R.Java with package name. Now the current situation is that I am bundling all resources into game resources with its package name. But the problem is that Unity Ads needs its own resources. How can I combine them in an assembly so that each plugin uses its own resources with its own package name and doesn't generate conflicts with dex classes?