question: Give the distinct department ids of departments in which a manager is in charge of 4 or more employees?
#1 return departments 
#2 return managers of  #1 
#3 return employees of  #2 
#4 return number of #3 for each #2 
#5 return #1 where  #4 is  4 or  more 
#6 return department ids of  #5 
#7 return distinct #6