# What is *length*?

**Length**is a measure of distance. The length of something is the distance between its two ends. Small length is called short and big length is called long. For two or three dimensional things, length is usually the longest side or edge.

## Input

**Light-year**is a unit of length used to express astronomical distances and is exactly equal to 9 460 730 472 580 800 meters.

## Output

**Millimeter**is a metric unit of length equal to one-thousandth of a meter.