Definition: 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: April took a vacation to Ireland. Sentence 2: There, she toured an old castle used during medieval times. Sentence 3: She marveled at the width and height of the fortress. Sentence 4: When the tour was completed, she stayed behind in the castle. Sentence 5: There she stared up at the castle walls until the end of the day. Choices: a. Fortress. b. Robot surprise.

a