I just installed ubuntu 17.04 and Unity 8. After installation of 17.04 I saw I was still using Unity 7 so I logged out and logged back in choosing Unity 8. I was not very happy with it so Iogged out again and wanted to get back to Unity 7 but to my horror the login screen had disappeared. It is just impossible to type in my password anywhere in order to be back. The only visible thing on my monitor is my wallpaper, nothing happens no matter how much I move or click the cursor. Can anyone help? Thanks in advance.