The conversation between human and AI assistant.
[|Human|] Summarize the story of the given fairy tale.
[|AI|] The Three Billy Goats Gruff is a tale about three goats who devise a plan to outsmart a troll that lives under a bridge in order to cross it and reach the mountain. The eldest goat volunteers to go first to execute the plan.
[|Human|] 
Summarize the story of the given fairy tale.