Question: Besides the length of Charles Grethen's primary race event, which two race lengths are standard in middle-distance running?

full_context: Document 1: Track and field: Track and field is a sport which includes athletic contests established on the skills of running, jumping, and throwing. The name is derived from the sport's typical venue: a stadium with an oval running track enclosing a grass field where the throwing and jumping events take place. Track and field is categorised under the umbrella sport of athletics, which also includes road running, cross country running, and race walking.
Document 2: Middle-distance running: Middle-distance running events are track races longer than sprints, up to 3000 metres. The standard middle distances are the 800 metres, 1500 metres and mile run, although the 3000 metres may also be classified as a middle-distance event. The 1500 m came about as a result of running three and 3/4 laps of a 400 m outdoor track or 7 and a half laps of a 200m indoor track, which were commonplace in continental Europe in the 20th century.
Document 3: 4 × 400 metres relay: The 4 × 400 metres relay or long relay is an athletics track event in which teams consist of four runners who each complete 400 metres or one lap. It is traditionally the final event of a track meet. At top class events, the first 500 metres is run in lanes. Start lines are thus staggered over a greater distance than in an individual 400 metres race; the runners then typically move to the inside of the track.
Document 4: 5K run: The 5K run is a long-distance road running competition over a distance of five kilometres (3.1 miles). Also referred to as the 5K road race, 5 km, or simply 5K, it is the shortest of the most common road running distances. It is usually distinguished from the 5000 metres track running event by stating the distance in kilometres, rather than metres.
Document 5: Charles Atsina: Charles Buaku Atsina Junior He is a Ghanaian and Italian naturalized professional footballer resident in London and currently playing for Vllanzia in the Albanian Superliga.Born on the 24th March 1989, grew up in Italy where he started his Football academy coached by Vittorio Zerpelloni http://www.calciatori.com/calciatore/zerpelloni-vittorio who was also a professional player from the Italian serie A&B.Atsina speaks four European languages Italian,English,Spanish and German In 2012, he joined AD Alcorcon The Liga Adelante, The 2nd Division club in Madrid With a Deal of €250k for a 1/2year deal plus 1year option,2013 discovered by the scout of Vfl Wolfsburg Frank Benatelli ex professional player and currently coach of Csv Bochum, In 2014, he joined the German side Csv Bochum with 24 appearance 20 goals And 7 Goals in The kreispokal. In 2015, he joined Tus Ennepetal with 22 appearance 5goals in the league and 5goals just in the 1st game of kreispokal https://www.derwesten.de/sport/lokalsport/ennepetal-gevelsberg-schwelm/widerstand-haelt-nur-eine-stunde-id9963722.html. Currently playing for the Finnish club Käpylän Pallo based in Helsinki. A very well known player in Bochum (Germany)for his record goals
Document 6: Charles Geerts (businessman): Charles Ludovicus Geerts (born 1943, in Amsterdam) is one of Amsterdam's largest brothel owners. In 2008 he sold 17 properties for 25 million EUR of which more than half was paid by the municipality. "Dikke Charles" (fat Charles), sometimes called "Amsterdam's Emperor of Sex," is a legendary king of brothels that before the sales controlled over 60 window brothels in the entertainment blocks. Most of the window brothels are now empty and curtains hang behind the windows.
Document 7: 400 metres: The 400 metres, or 400 metre dash, is a common sprinting event in track and field competitions. It has been featured in the athletics programme at the Summer Olympics since 1896 for men and since 1964 for women. On a standard outdoor running track, it is one lap around the track. Runners start in staggered positions and race in separate lanes for the entire course. In many countries, athletes previously competed in the 440 yard dash (402.336 m)—which is a quarter of a mile and was referred to as the 'quarter-mile'—instead of the 400 m (437.445 yards), though this distance is now obsolete. An athlete who competes in the 400 m may still be referred to as 'quarter-miler'; the distance or event might still be called the "quarter."
Document 8: List of European Athletics Championships records: The European Athletics Championships is a quadrennial event which began in 1934. European Athletics accepts only athletes who are representing one of the organisation's European member states and the body recognises records set at editions of the European Athletics Championships. The Championships records in athletics are the best marks set in competitions at the event. The athletics events at the Championships are divided into four groups: track events (including sprints, middle- and long-distance running, hurdling and relays), field events (including javelin, discus, hammer, pole vault, long and triple jumps), road events and combined events (the heptathlon and decathlon).
Document 9: Cédric Charlier: Cédric Charlier (born November 27, 1987) is a Belgian international field hockey player. At the 2008, 2012 and 2016 Summer Olympics, he competed for the national team in the men's tournament. At the 2016 Olympics, he was part of the Belgian men's team that won the silver medal. Charlier also won silver with Belgium at the 2013 European Championship on home ground in Boom.
Document 10: Charles Grethen: Charles Grethen (born 2 June 1992 in Tuntange) is a Luxembourgian middle-distance runner competing primarily in the 800 metres. He represented his country at three consecutive European Championships.
Document 11: 3000 metres steeplechase: The 3000 metres steeplechase or 3000-meter steeplechase is the most common distance for the steeplechase in track and field. It is an obstacle race over the distance of the 3000 metres, which derives its name from the horse racing steeplechase.
Document 12: Che Mian: He competed in the 2004 Summer Paralympics in Athens, Greece. There he won a silver medal in the men's 4 x 100 metre relay - T35-38 event, a silver medal in the men's 4 x 400 metre relay - T35-38 event, a bronze medal in the men's 100 metres - T36 event, finished sixth in the men's 200 metres - T36 event and finished fourth in the men's 400 metres - T36 event. He also competed at the 2008 Summer Paralympics in Beijing, China. There he won a silver medal in the men's 4 x 100 metre relay - T35-38 event, a bronze medal in the men's 200 metres - T36 event, a bronze medal in the men's 400 metres - T36 event and finished sixth in the men's 100 metres - T36 event
Document 13: Christoph Herle: Christoph Herle (born 19 November 1955 in Königstein im Taunus, Hessen) is a retired West German long-distance runner who specialized in the 10000 metres and cross-country running. His first major international track race occurred in the 1978 European Athletics Championships in Prague, former Czechoslovakia, where he placed fourteenth in the 5,000-metre final (see Tapio Pekola et al., eds., "European Championships Prague" / EM-Praha, Kaarina, Finland: Publications Company Runner / Juoksija, 1978). He ran slightly better in the 1982 European Athletics Championships 5,000-metre final in Athens, Greece, placing thirteenth (see Markku Siukonen and Matti Aho, eds., "The Great European Championships Book" / Suuri EM-kirja, Jyväskylä, Finland: Sportti Kustannus / Sport Publications Oy / Ltd., 1990). Herle ran best in 1983 and 1984, placing eighth at the 1983 World Athletics Championships 10,000-metre final in Helsinki, Finland (see, for example, Mikko S. Laitinen et al., eds., "World Athletics Championships 1983" / Yleisurheilun maailmanmestaruuskilpailut 1983, Salt Lake City, Utah, USA: International Sport Publications, 1983), and fifth at the 1984 Summer Olympics 10,000-metre final in Los Angeles, the United States (see, for example, "The Big Olympic Book 4" / Suuri Olympiateos 4, published in Finland in 1984). He never managed to rise to the very top of international long-distance runners, however. His final major international championships race was the 1986 European Athletics Championships 10,000-metre race in Stuttgart, then West Germany, where he placed a disappointed fifteenth (see Siukonen and Aho, eds., "The Great European Championships Book").
Document 14: Mehdi Baala: Mehdi Baala (Arabic: مهدي بعلة‎ ‎ ; born 17 August 1978 in Strasbourg) is a French, middle-distance runner competing mainly in the 1500 metres event. Baala has won several major international championships medals in the 1500 metres event – an Olympic Games bronze, a World Championships silver, two European Championships golds and a European Indoor Championships bronze. Moreover, he has won several medals in the 1500 metres event of the European Cup, IAAF World Cup and the IAAF World Athletics Final. Baala is considered to be the best French middle-distance runner of all time. As of July 2013, he holds French national outdoor records for four distances (800m: 1.43.15, 1000m: 2.13.96, 1500m: 3.28.98 and 2000m: 4.53.12; all of these were set from 2002 to 2005) and French national indoor records for four distances (800m, 1000m, 1500m and the mile; all of these were set from 2003 to 2009).
Document 15: 800 metres: The 800 metres, or 800 meters (US spelling), is a common track running event. It is the shortest common middle-distance running event. The 800 metres is run over two laps of the track (400 metre track) and has been an Olympic event since the first games in 1896. During indoor track season the event is usually run on a 200-metre track, therefore requiring four laps.
ground_truth: 1500 metres and mile