an IF formula possibility?

I have been searching in here for a certian formula but I cannot seem to be able to find it so I am sorry if this has been asked before.

I am trying to create a formula that cancels each other out.. I know, im not making sense so bear with me.

lets say i have 15 apples in column A
I also have 15 apples in column m

I want to have a formula that I can tell it to erase both spots if they match (ie. if a1=am then erase)