Biathlon is a winter sport, a combination of cross-country skiing and rifle shooting. Another variant of this sport is summer biathlon, which is a combination of cross-country running and rifle shooting. The race consists of participants skiing around a cross-country trail system. The total distance is broken into two or four shooting rounds, half in standing position and the other half in prone position. An extra time is added to the participant's total running time depending on his or her shooting performance. In each shooting round, the participants must hit five targets. If the participant misses a target, this should be "atoned for" in 3 ways: skiing around a 150-meter penalty loop, add one minute to the skier's total time, or use an extra cartridge to finish the target. Split times are taken at several points so we can keep track of the participants' progress. Biathlon is an official event at the Winter Olympics.