I asked my prolog what the value of N was and it told me:
Welcome to SWI-Prolog (Multi-threaded, Version 5.6.14) Copyright (c) 1990-2006 University of Amsterdam. SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it under certain conditions. Please visit http://www.swi-prolog.org for details.
For help, use ?- help(Topic). or ?- apropos(Word).
?- N. % ... 1,000,000 ............ 10,000,000 years later % % >> 42 << (last release gives the question)
