Instructions: 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.
Input: Title: Pop Quiz. Sentence 1: He figured he could just catch up at the last minute. Sentence 2: Tom had not been keeping up with his reading for class. Sentence 3: At the beginning of class his teacher gave a pop quiz. Sentence 4: Tom was completely unprepared for it. Sentence 5: He failed it pretty badly.
Output:
21