Mass start

Mass start is a format of starting in some events in athletics (track and field), such as a marathon race, speedskating or a long-distance cross country skiing competition.
There are usually a large number of competitors in such an event, and in order for all the competitors to have the same environmental conditions, which, among other things, include temperature, wind speed, rain or shine, etc., they need to start at the same time and same place and proceed along the same course. But the large number of competitors makes it impossible to fit all of them at the same starting line. So the athletes stand in a pack before they begin: some are behind others, sometimes by dozens of meters or more, depending on the number of competitors.
The tradition is that all the athletes start at the same time, the gun time, and use the same starting line and same finishing line as those in the front of the pack. This means that those in the back of the pack have to run an extra distance...