Excel 2013 Formula - maybe IF formula?

I have a list of names in Excel and I need to put their supervisor name in the cell to the right of each name. I would like to find a formula that will automatically check each name and depending on that name put their supervisor name in the cell to the right. There are duplicates in the name list. Is this possible?

What I have so far is: =IF(A1:A19="John","Deb") I have been copying the formula down the list and it puts Deb by all the John names - but I would have to keep changing the formula for each name and supervisor name and copy it into each cell over and over - that doesn't seem very efficient to me.

Any help you can give me would really be appreciated. Thank you.