Do I have to buy two Unity3D to develop for Android and iPhone?

I want to develop an app for both android and iPhone simultaneously. Do I need to purchase two separate copies (licenses and actual operating system versions) of the Unity3D to accomplish that or does buying one license come with both operating systems version of Unity? I surely hope the latter is the case.

Thank you

There is only one Unity program, but iOS publishing and Android publishing are two separate licenses.