How long is a marathon?
A marathon is a long-distance running race with an official distance of 42.195 kilometers (26 miles 385 yards), usually run as a road race.
Complete the following task based on the instruction and optional input provided.### Instruction:
How long is a marathon?

### Output:
A marathon is a long-distance running race with an official distance of 42.195 kilometers (26 miles 385 yards), usually run as a road race.