Recently, I have installed ubuntu 13.04, and updated it. I want to install skype. I search in "ubuntu software center" but I did not find anything. Therefore, I search on internet. I found out some commands for skype installation. Then, I open the terminal and type the command. it request for password. The problem is that when i want to enter my password, my keyboard did not work and I can not type my password. How can I fix that?