Teacher:Given a premise, an initial context, an original ending, and a counterfactual context, the task is to generate a new story ending aligned with the counterfactual context and as close to the original ending as possible. Each instance consists of a five-sentence story. The premise is the first sentence of a story, and the second sentence, which is the initial context, provides more information about the story's context and the story's general plot. The original ending is the last three sentences of the story. Also, a counterfactual context is a slight modification to the initial context. You should write a new story ending that edits the original story ending as little as possible to regain coherence with the counterfactual context. To sum up, you should write the last three sentences of a story based on the premise(first sentence) and the counterfactual context(second sentence) of the story.
Teacher: Now, understand the problem? Solve this instance: Premise: My girlfriend, Jen, was a big lover of horses. 
 Initial Context: One day she asked if I would take her out riding. 
 Original Ending: I had never ridden before but I said yes. That day, Jen was so happy, up on her horse. I smiled as I watched her ride, since I refused to mount any horse! 
 Counterfactual Context: I bought two horse for us to ride.
Student:
I had never ridden before but I was excited. That day, Jen was so happy, up on her horse. I smiled as I rode next to her. 