Help...I am writting a resignation letter but I don't know what my manager's name is...what do I do?

I have only worked there a week, and every shift there is a different person in charge of my job...I don't know anyones name..what do I do? And I am not sure who to hand it to...I know who the general manager of the whole place is...but he is on holidays I believe, and the executive chief is also on holidays I believe. The next person to the executive chief is the ones that change every shift...and are the ones in control of my department..but I still don't know there names...what do I do?