March 2012 Fiendish Function

The Fiendish Function posed during March 2012 had the following sample guesses and replies:

• GUESS
• REPLY
• 1
• 5
• 2
• 5
• 3
• 4
• 4
• 4
• 5
• 4
• 10
• 5

The rule was: "Count the number of letters in the word for the number, then count the number of letters in the word for that number".

Suppose the guess was 19:

• Count the number of letters in "nineteen", giving 8.
• Count the number of letters in "eight", giving 5.

So the result is 5.