Task: Story Composition
Input (English): Premise: Mitch was planning his 50th birthday party. 
 Initial Context: To make it special he decided to invite 50 of his friends. 
 Original Ending: He went to the post office to buy 50 stamps. The post office worker asked about the purpose of the stamps. Mitch told him about the party and gave him the first invite. 
 Counterfactual Context: To make it special he decided to invite his best friend.
Output (English): He went to the post office to buy stamps. The post office worker asked about the purpose of the stamps. Mitch told him about the party and gave him the first invite.