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: What is the most important prognostic factor in Stage 1 Melanoma?
Options: <1> Serum LDH level. <2> Tumor thickness measured in the Breslow index. <3> The presence of clinical or histological ulceration. <4> Number of metastases. <5> The mitotic index. The mitotic index.
Output:
2