Deciphering a substitution cipher

I wrote a program that runs Gibbs sampling to decode an encrypted message. The message is crypted using a simple substitution cipher. The program randomly tries different keys and incrementally constructs keys that maximize the score of the decoded message according to a trigram language model. The number indicates how many ciphers have been tried thus far. The message of course is an excerpt from The ones who walk away from Omelas by Ursula K. Leguin.