June 2016 Fiendish Function

The Fiendish Function posed during June 2016 had the following sample guesses and replies:

• GUESS
• REPLY
• 1
• 15
• 2
• 20
• 3
• 20
• 4
• 6
• 5
• 6
• 10
• 20

The rule was: "Convert the first letter in the word for the number using a=1, b=2, etc".

Suppose the guess was 17:

• Convert the first letter of "seventeen" using a=1, b=2, etc giving 19.

So the result is 19.