Definition: You are given a paragraph, with numbered sentences, and a question. Write the numbers of the sentences needed to answer the given question. Separate multiple sentence numbers with a comma (", "). E.g. "1, 2" would be the correct response if Sent 1 and Sent 2 are needed to answer the given question (do not include sentences that contain no information that is necessary to answer the question). Sort the sentence numbers in an increasing order (i.e., '1, 2', instead of '2, 1'). Your answer should not contain anything than the sentence numbers separated by a comma (e.g. '1, 2, 3, 4'). The given question requires more than one sentence to answer. So, your answer must contain at least one comma (", ").
Input: Paragraph- Sent 1: They parted and Allan made his way pensively from Arthur's gate.
Sent 2: He walked the wheel-ruts, hands in his pockets and unshined shoes collecting dust.
Sent 3: Some quarter-mile from Arthur's gate, he halted, confronted by a halloo.
Sent 4: "Nathan?"Sent 5: he called out to the empty road.
Sent 6: The reply came from above him and Allan turned to see his friend reclining in the fork of a great tree.
Sent 7: "I had a hunch you'd be at Arthur's today," said Nathan, "so I thought I'd wait here for you."Sent 8: Nathan's lanky frame, dressed in a loose, tan jacket, fit into the branch like an elegant skeleton.
Sent 9: His hair fell loosely across a face that seemed always to have a knowing smirk hidden just beneath its surface, infusing his body with a rakish energy.
Sent 10: "So, Allan," said Nathan, unfolding and lowering his legs to the roadside, "how goes life for the quintessential American author?"Sent 11: "I wouldn't know," replied Allan dryly, before continuing in another tone entirely.
Sent 12: "I destroyed another story last night, Nathan."Sent 13: Leaning against his tree, Nathan shook his head.
Sent 14: "You mean, finished another story."Sent 15: "Yes, it is finished!
Sent 16: Ended!
Sent 17: Never again shall it see the rosy-fingered dawn!
Sent 18: Nathan, you've read these abominations of mine.
Sent 19: You know just as well as I that they have no future, no potential.
Sent 20: At best, they are faery tales; at worst, expeditions into macabre realms no healthy mind need ever see.". 
Question: What does Allan mean when he says that he "destroyed another story last night?".
Output:
12, 14, 15.