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? If you are still confused, see the following example:
Premise: Susie was sitting on her barstool. 
 Initial Context: She kept kicking the counter with her feet. 
 Original Ending: Suddenly, her kick sent her falling backwards. The chair hit the ground with a thud and broke. Susie hurt her head and was really scared. 
 Counterfactual Context: She kept herself steady with her feet.
Solution: Suddenly, an earthquake sent her falling backwards. The chair hit the ground with a thud and broke. Susie hurt her head and was really scared.
Reason: The generated new ending is perfect. It considers the counterfactual context and changes required parts in original ending.

Now, solve this instance: Premise: The class watched the giant animal move across the field. 
 Initial Context: There was a huge bison right on the other side of the fence! 
 Original Ending: They watched him walk by and head down the hill. The class learned about how Native Americans used the bison. They felt very educated on Native American history. 
 Counterfactual Context: Too bad it wasn't a bison on the other side of the fence.
Student:
It was a moose instead, and they watched him walk by and head down the hill. The class learned about how Native Americans used the moose. They felt very educated on Native American history. 