Besides the length of Charles Grethen's primary race event, which two race lengths are standard in middle-distance running?
Charles Grethen: Charles Grethen (born 2 June 1992 in Tuntange) is a Luxembourgian middle-distance runner competing primarily in the 800 metres. Middle-distance running: Middle-distance running events are track races longer than sprints, up to 3000 metres.
i don't know