Gitto - if you Google A and 15 it’ll become clear.
For those wavering re: the final step - it depends on how rigidly you adhere to the definition of the first word of D.
If you decide that W, say, is equivalent, thematically, to F. say, you’ll get a different picture than if you decide that it isn’t.
Trust this is neither too, nor inadequately, cryptic, bizarrely.