Instructions: 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'.
Input: Sentence 1: Brian wanted to go to a concert with friends. Sentence 2: His boss would not let him have time off. Sentence 3: He decided to switch shifts with a coworker. Sentence 4: Brian went to the concert and had a great time. Sentence 5: Brian now owes his co worker a favor in the future. Choices: a. Proposal. b. Concert.
Output:
b