Definition: 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'.
Input: Question: The NR3 group of a quaternary ammonium salt, R NR3, is a good leaving group in reactions:
Options: <1> E1. <2> E2. <3> SN1. <4> SN2. <5> In none of the above.
Output:
2