def teacher_input(random_numbers):
  """
  Defines the contents of `teacher-input.txt` to which `run.sh`
  concatenates the student submission as the exercise is posted to
  MOOC Grader for grading.

  Generates 3 random numbers and forms a string containing
  the MathCheck configuration for this exercise.
  """

  return \
    u"arithmetic\n" + \
    u"f_nodes 3\n" + \
    u"{}/3^({}) + {}\n".format(random_numbers[0],random_numbers[1],random_numbers[2],)