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: How many people live in the city where Kirdorf was born? Passage 1:The First Indochina War had raged, as guerrilla warfare, since 19 December 1946. From 1949, it evolved into conventional warfare, due largely to aid from the communists of the People's Republic of China ("PRC") to the north. Subsequently, the French strategy of occupying small, poorly defended outposts throughout Indochina, particularly along the Vietnamese-Chinese border, started failing. Thanks to the terrain, popular support for August Revolution and support for decolonization from bordering China and the U.S.S.R., the Viet Minh had succeeded in turning a "clandestine guerrilla movement into a powerful conventional army", following asymmetric warfare theory laid by Mao Tse Tung, something which previously had never been encountered by the western colonial powers. In October 1952, fighting around the Red River Delta spread into the Thai Highlands, resulting in the Battle of Nà Sản, at which the Viet Minh were defeated. The French used the lessons learned at Nà Sản – strong ground bases, versatile air support, and a model based on the British Burma Campaign – as the basis for their new strategy. The Viet Minh, however, remained unbeatable in the highland regions of Vietnam, and the French "could not offset the fundamental disadvantages of a roadbound army facing a hill and forest army in a country which had few roads but a great many hills and forests".
 Passage 2:On 29 April 1992, a group of Junior soldiers in the Sierra Leone Army led by a 25 year old Captain Valentine Strasser overthrew President Momoh, and Sierra Leone was under Military rule from 1992 to 1996 during the civil war. Sierra Leone returned to a democratically elected government when the military Junta under Brigadier General Julius Maada Bio who had ousted Strasser in a coup in 1996, handed the presidency to Ahmad Tejan Kabbah of the SLPP after his victory in the 1996 Sierra Leone presidential election. However, on 25 May 1997, the Sierra Leone military overthrew President Kabbah in a coup and Major General Johnny Paul Koroma became the country's Head of State. However, in February 1998, a coalition of West African Ecowas armed forces led by Nigeria reinstated President Kabbah by military force, and the leaders of the coup were executed after they were sentenced to death by a Sierra Leone military court. In January 2002, President Kabbah announced the ending of the civil war with the help and support of Ecowas, the British government, the African Union, and the United Nations. Sierra Leone has had an uninterrupted democratic government from 1998 to present.
 Passage 3:Emil Kirdorf was born at Mettmann, Rhine Province. His father was a wealthy owner of a weaving mill. He had a brother named Adolf who would be his business partner during his adult life. Kirdorf volunteered a year in 1864 in Hamburg to work in an export enterprise. A year later, he worked in a textile company in Krefeld. The family's mill went bankrupt, mainly because of the management's refusal to introduce mechanical looms. Kirdorf therefore changed to mining industry in which he worked as an accountant. Following the Franco-Prussian War, he became director of Zeche Holland in 1871. Two years later, the entrepreneur Friedrich Grillo offered him the position of commercial director in the Gelsenkirchener Bergwerks-AG (GBAG) company. He became general manager of GBAG in 1893. He steered the company through the Long Depression of the 1870s, and held this position until 1926.
3