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: The Terrific Treehouse. Sentence 1: Mark got some friends together to build it all in one day. Sentence 2: He drew up plans for an excellent tree house to build in the backyard. Sentence 3: Mark decided he wanted to surprise his son with a cool gift. Sentence 4: When Mark's son got home from school, Mark showed him the gift. Sentence 5: The boy was incredibly surprised and thrilled at the amazing present.
Output:
31