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.
Q: Premise: Bob walked down the hall in the building where he worked. 
 Initial Context: His friend Joe came around the corner and walked with Bob. 
 Original Ending: They didn't say anything to each other. Once they had a large hall in front of then, Bob gave a nod. On cue, Bob and Joe began a foot race to the end of the hall. 
 Counterfactual Context: His friend Chelsea came around the corner and walked with Bob.
A: 
They didn't say anything to each other. Once they had a large hall in front of then, Bob gave a nod. On cue, Bob and Chelsea began a foot race to the end of the hall. 