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: Midway. Sentence 1: Aircraft carriers were her only major offensive weapon. Sentence 2: America was still reeling from Japan's surprise attack. Sentence 3: They sent them all to drive the Japanese off of Midway Island. Sentence 4: There was a week long air and sea battle. Sentence 5: Finally the Americans won the island.
A:
21