The Hitchhiker's Guide to the Galaxy (Hitchhiker's Guide, #1)

by Douglas Adams

This planet has—or rather had—a problem, which was this: most of the people living on it were unhappy for pretty much of the time. Many solutions were suggested for this problem, but most of these were largely concerned with the movements of small green pieces of paper, which is odd because on the whole it wasn’t the small green pieces of paper that were unhappy.

R is a velocity measure, defined as a reasonable speed of travel that is consistent with health, mental well-being and not being more than, say, five minutes late.