How to bring the HOD name in compensation worksheet?

Summary:

Head Of Departments are attached to child nodes of the department tree with help of AOR. Customer's ask is to print the HODs name in promotion letter, hence need to bring the name to Comp Worksheet Custom Column.

i understand it can be done using the default override formula but I do not have a sample formula to bring the person name as in this case.

Any help is highly appreciated.