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 employees ( department_id VARCHAR, manager_id VARCHAR, employee_id VARCHAR )

### Question ###
Find the ids of the departments where any manager is managing 4 or more employees.

### Accurate SQL ###

SELECT DISTINCT department_id FROM employees GROUP BY department_id, manager_id HAVING COUNT(employee_id) >= 4