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: Inside Job. Sentence 1: Gary immediately suspected one of his roommates. Sentence 2: Gary's house was recently robbed. Sentence 3: Gary's alarm did not go off, so he knew it was an inside job. Sentence 4: Gary was mad that his own roommates would rob his house. Sentence 5: Gary felt so violated that his house was robbed.
A:
21