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'.

Example Input: Sentence 1: Ethan's friends challenged him to drink 2 liters of cola in an hour. Sentence 2: They pooled their funds and offered him twenty dollars. Sentence 3: Ethan accepted the challenge. Sentence 4: He struggled, but he managed to drink all the cola on time! Sentence 5: However, that night Ethan had a terrible stomach ache! Choices: a. Challenge. b. Slow in understanding.
Example Output: a

Example Input: Sentence 1: Kenny was a teacher at a local school. Sentence 2: His students weren't doing as well as they should have. Sentence 3: Kenny told his students he'd give them pizza if their grades improved. Sentence 4: The children did much better on their next exam. Sentence 5: Kenny treated the children to pizza. Choices: a. Record. b. The Incentive.
Example Output: b

Example Input: Sentence 1: Tom got a new dog. Sentence 2: It was not housebroken. Sentence 3: Tom often found his apartment messed up. Sentence 4: He tried hard to train him to no avail. Sentence 5: Tom wound up getting rid of it. Choices: a. Bad Dog. b. Inflatable Bed.
Example Output:
a