Lamp Brightness Menu

A lamp has a brightness from 0 to 3, starting at 0. Show the menu 1) Brighter, 2) Dimmer, 3) Show, 4) Quit and read the choice with the prompt Choice: , stripped. Choice 1 adds one and prints Brightness: <n>, unless it is already 3, in which case print Already at maximum. and change nothing; choice 2 subtracts one and prints the same line, unless it is already 0, in which case print Already off.; choice 3 prints Brightness: <n>; choice 4 prints Goodbye! and leaves the loop; anything else prints Unknown choice - try again.. Input: one choice per line, ending with 4. The prompt is part of the output, so each message follows Choice: .