Reinstall ROS

I accidentally deleted cv_bridge when trying to compile the code for SLAM. I should have read the packages that will be deleted when I installed libjpeg in synaptics. 

Anyway, libjpeg destroys the cv_bridge package in my ROS Indigo. I could not install it back from synaptics either. 

The problem was solved by reinstall ROS Indigo, by the command from here. 

sudo apt-get install ros-indigo-desktop-full