Q: In this task, you're given the title of a story consisting of five sentences, numbered 1 through 5. Your job is to determine which two sentences need to be swapped sentences in order to make a story that makes complete sense and is befittingly titled. Indicate your answer using the numbers of the two sentences in order, such as '34' or '25'. The first digit refers to the sentence which should come first in the story.
Title: Sleep On This. Sentence 1: She screamed and flicked it off. Sentence 2: A spider dropped on to Xena's leg. Sentence 3: Then another one landed almost where the first had been. Sentence 4: Xena saw they were dropping from the light fixture above her. Sentence 5: She jumped up and dived into her shower.
A:
21