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.
Q: Title: making coffee. Sentence 1: Then, it filtered through the coffee grounds. Sentence 2: The water heated up in the tank. Sentence 3: Anna waited for the coffee to brew. Sentence 4: The coffee dripped into the pot. Sentence 5: The coffee pot was finally full of coffee.
A:
13