Now, the system is used for either one of two things. It's either used in determining the absolute configuration of your enantomers to either R or S absolute configuration, or it's used to help you rank groups attached to double bonds. So in this lecture, we're going to focus primarily on this usage here. So whenever you're using this system, four important rules must be followed that will help you to get or find the highest priority groups. So let's look at rule number one. So, atom with higher atomic number receives higher priority.