Cant find root folder for android SDK

I open preferences and go to external tools and click on the browse button next to android SDK. It then opens up the file explorer with my Program Files. I select the Android folder but the file explorer closes and reopens back to the program files page. And the android SDK has not been connected. This also happens for any sub folder within Android and when I try to select any random folder. Please help me connect my SDK to unity because I really want to start developing android games.

if u instaled your sdk manager from Sdk Web page it shoud be working,but if u dowlnoaded from another website your Sdk floder shoud be where u extract it find that place and put it inexternal tools .