Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE department ( head VARCHAR, departmentID VARCHAR )

### Question ###
What is the employee id of the head whose department has the least number of employees?

### Accurate SQL ###

SELECT head FROM department GROUP BY departmentID ORDER BY COUNT(departmentID) LIMIT 1