Given the task definition and input, reply with output. 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: Who were the first commander of the regiment Erwin served in during the American Civil War? Passage 1:The source of the river is Lake Hendricks on the boundary of Lincoln County, Minnesota, and Brookings County, South Dakota. It issues from the lake in Hendricks, Minnesota, and flows northeastwardly through northwestern Lincoln County as an intermittent stream on the Coteau des Prairies, a morainic plateau dividing the Mississippi and Missouri River watersheds, into western Yellow Medicine County, where it flows off the Coteau, dropping 250 feet (76 m) in eight miles (13 km). Continuing northeastwardly through flat till plains with occasional willows and cottonwoods along its banks, the river flows into eastern Lac qui Parle County, passing to the east of Dawson. It flows into the Minnesota River just below Lac qui Parle Lake in Lac qui Parle State Park, approximately ten miles (15 km) northwest of Montevideo, after flowing through a wooded valley in which it drops 210 feet (64 m) in 18 miles (29 km). Lac qui Parle Lake was formed by a delta at the mouth of the Lac qui Parle River, and is maintained by a dam.
 Passage 2:During the 2006/07 season, Liang reached at least the second round of qualifying in every ranking event. At the Northern Ireland Trophy, he beat Robert Stephen 5–0 before falling to David Gilbert 0–5 in qualifying. However, at the Grand Prix, Liang came top of his qualifying group, above more experienced players such as Gerard Greene and Barry Pinches. He finished fourth in his group at the round-robin stage, and although he did not progress to the next round, he did beat former world champion and world number one Stephen Hendry 3–0. At the UK Championship, he lost in the second round of qualifying to Jamie Burnett 7–9. In the following ranking event, the Malta Cup, he lost to Joe Jogia 3–5, again in the second round of qualifying. He qualified for the Welsh Open, his third ranking tournament, by beating Dene O'Kane, Joe Jogia and Mark Davis. He met Nigel Bond again in the last 48, this time losing only 3–5.
 Passage 3:Born in Washington, Lycoming County, Pennsylvania, Erwin settled in Portage, Wisconsin in 1853. From 1855 to 1868, Erwin lived in Jo Daviess County, Illinois and then in Stephenson County, Illinois. During the American Civil War, Erwin served in the 45th Illinois Volunteer Infantry Regiment. In 1868, Erwin moved to Tomah, Wisconsin and was in the mercantile business. From 1879 to 1882 and 1886, Erwin served on the Tomah Board of Education and was president of the school board. From 1882 to 1889, Erwin served in the Wisconsin State Senate and was a Republican. In 1889, Erwin served as postmaster for Tomah, Wisconsin. In 1902, Erwin moved with his family to Milwaukee, Wisconsin. Erwin died suddenly in Savanna, Illinois just as he was about get on a train for a trip to Omaha, Nebraska.
3