Teacher:In this task, you're given four sentences of a story written in natural language in which one part is missing. Your job is to predict the position and missing part of the story and return in the following format: position, missing part. The missing part is a sentence that completes the story, and the position is the number of the missing sentence in the new story.
Teacher: Now, understand the problem? Solve this instance: Sentence1: They both needed to use the school library books about dolphins. Sentence2: But Mary had beaten Gina and taken them all. Sentence3: And now she refused to share the books. Sentence4: Gina's mother had to call Mary's mom to complain.
Student:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
1, Gina's friend Mary wouldn't share.