You will be given a definition of a task first, then some input of the task.
In this task, you're given five sentences, numbered 1 through 5, and two options a and b for possible titles for the story. Your job is to choose the title that better fits the story. Indicate your choice by 'a' or 'b'.

Sentence 1: Tim was heating up food for lunch. Sentence 2: He used the break room microwave. Sentence 3: He messed up and put too much time on. Sentence 4: After a while it overheated and blew up. Sentence 5: The office had to be evacuated. Choices: a. Small Explosion. b. Doored.
Output:
a