You will be given a definition of a task first, then some input of the task.
In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: In what disorder of eating behavior, the personality of patients is characterized as impulsive people, with a tendency to make quick decisions and act unpredictably?
Options: <1> Anorexia nervosa of restrictive type. <2> Pica. <3> Obesity. <4> Bulimia nervosa. <5> Night dining
Output:
4