Absence Approval rule for top employee

Summary:

Absence Approval rule for top employee

Content (please ensure you mask any confidential information):

I have currently setup approval rule for Emp, MGR and HR for Global Absence approval where the rule follow below path -
Approval: Department Head (handling this through AOR)
FYI: Line Manager
When the top employee of organization chart applies leave he rule fails stating that supervisor record is missing for employee, can someone help me on how to setup the approval rule to exclude the top employee using Grade, Position, Job etc..,

Version (include the version you are using, if applicable):

2D

Code Snippet (add any code snippets that support your topic, if applicable):