Convert from span to story

Unit Definition (span)
Span is the width of a human hand, from the tip of the thumb to the tip of the pinky finger.

Unit Definition (story)
The story is an informal unit of distance equal to the average distance between floors of a building. In British English the spelling is "storey" and the plural is "storeys"; Americans write "story" and "stories." Typically a story equals 10 to 12 feet (3.0-3.6 meters). The origin of this use of the word "story" is not entirely clear, but in medieval times a tier of sculptures or stained glass windows on the front of a cathedral was called a stor(e)y because it usually told a story, and the number of stories was a measure of the size of the building.