You will be given a definition of a task first, then some input of the task.
In this task, you're given a question, along with three passages, 1, 2, and 3. Your job is to determine which passage can be used to answer the question by searching for further information using terms from the passage. Indicate your choice as 1, 2, or 3.

Question: How many miles long is the river that Silvanus drove the Alamanni tribesmen back from? Passage 1:Like the star Epsilon Draconis in the constellation of Draco, Beta Cephei is visible primarily in the northern hemisphere, given its extreme northern declination of 70 degrees and 34 minutes. It is nevertheless visible to most observers throughout the world reaching as far south as cities like Harare in Zimbabwe, Santa Cruz de la Sierra in Bolivia or other settlements north ± 19° South latitude. It is circumpolar throughout all of Europe, northern Asia, and North American cities as far south as Guadalajara in west central Mexico. All other locations around the globe having a latitude greater than ± 20° North will notice that the star is always visible in the night sky. Because Beta Cephei is a faint third magnitude star, it may be difficult to identify in most light polluted cities, though in rural locations the star should be easily observable.
 Passage 2:After the outbreak of the Great War, Thommée joined the 276th Infantry Regiment and served with distinction as a commanding officer of a company and then battalion. In 1916 he was promoted to the rank of lieutenant colonel and became an adjutant at the staff of the 48th Corps in the area of the Romanian front. After the Russian Revolution of 1917, he quit the army and on 25 September 1918 he joined the Polish Army in the area of Kuban. There, on 9 November he became the de facto chief of staff of Lucjan Żeligowski's Polish 4th Rifle Division, formally a part of the Polish Blue Army allied to France, United Kingdom, U.S. and Imperial Russia. After the division returned to Poland and was reformed into the 10th Infantry Division, Thommée served as the chief of its staff during the opening stages of the Polish-Bolshevik War until August 1919. On 22 August that year he became the head of the Third department of the staff (Offensive intelligence "B"), controlling the intelligence net in the European part of Russia, at the North-Western Front, Masovian Front and then the Polish 1st Army under Gen. Franciszek Latinik.
 Passage 3:Silvanus was born in Gaul, the son of Bonitus, a Laetic Frankish general who had supported Constantine I in the civil war against Licinius. Like so many other Franks of his times, and like his father before him, he was a loyal and thoroughly romanized "barbarian" in the military service of the Empire. By AD 351, he held the rank of tribune and was one of the senior officers who defected to Emperor Constantius II at the Battle of Mursa Major, after initially supporting the usurper Magnentius. An able soldier, Silvanus was eventually promoted to the rank of Magister militum per Gallias, a crucial post, then in AD 352-353, Constantius personally entrusted him with the difficult task of driving the Alamanni tribesmen raiding and looting in Gaul back beyond the Rhine, and restoring the fast eroding Roman authority in the province. This Silvanus fulfilled partly by bribing the Alamanni chieftains with the taxes he had collected, partly by defeating the Alamanni in battle and partly by suppressing the local bagaudae insurrections flaring up again in central and northern Gaul.

Output:
3