Q: 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 (", ").
Paragraph- Sent 1: Alexander's army crossed the Hellespont in 334 BC with approximately 48,100 soldiers, 6,100 cavalry and a fleet of 120 ships with crews numbering 38,000, drawn from Macedon and various Greek city-states, mercenaries, and feudally raised soldiers from Thrace, Paionia, and Illyria.
Sent 2: (However, Arrian, who used Ptolemy as a source, said that Alexander crossed with more than 5,000 horse and 30,000 foot; Diodorus quoted the same totals, but listed 5,100 horse and 32,000 foot.
Sent 3: Diodorus also referred to an advance force already present in Asia, which Polyaenus, in his Stratagems of War (5.44.4), said numbered 10,000 men.) He showed his intent to conquer the entirety of the Persian Empire by throwing a spear into Asian soil and saying he accepted Asia as a gift from the gods.
Sent 4: This also showed Alexander's eagerness to fight, in contrast to his father's preference for diplomacy.
Sent 5: After an initial victory against Persian forces at the Battle of the Granicus, on the 24 of Daisios (8 April 334 BC), Alexander accepted the surrender of the Persian provincial capital and treasury of Sardis; he then proceeded along the Ionian coast, granting autonomy and democracy to the cities.
Sent 6: Miletos, held by Achaemenid forces, required a delicate siege operation, with Persian naval forces nearby.
Sent 7: Further south, at Halicarnassus, in Caria, Alexander successfully waged his first large-scale siege, eventually forcing his opponents, the mercenary captain Memnon of Rhodes and the Persian satrap of Caria, Orontobates, to withdraw by sea.
Sent 8: Alexander left the government of Caria to a member of the Hecatomnid dynasty, Ada, who adopted Alexander.
Sent 9: From Halicarnassus, Alexander proceeded into mountainous Lycia and the Pamphylian plain, asserting control over all coastal cities to deny the Persians naval bases.
Sent 10: From Pamphylia onwards the coast held no major ports and Alexander moved inland.
Sent 11: At Termessos, Alexander humbled but did not storm the Pisidian city.
Sent 12: At the ancient Phrygian capital of Gordium, Alexander "undid" the hitherto unsolvable Gordian Knot, a feat said to await the future "king of Asia".
Sent 13: According to the story, Alexander proclaimed that it did not matter how the knot was undone and hacked it apart with his sword.
Question: How did Alexander the Great undo the Gordian Knot?.
A:
12, 13.