You will be given a definition of a task first, then some input of the task.
In this task, you're given the title of a five-sentence story and the first four sentences. Your job is to write the last sentence of the story such that it seamlessly connects with the rest of the story.

Title: Seriousness. Sentence 1: Charles was a very serious man and didn't laugh a lot. Sentence 2: His friends tried to tell jokes but he remained untouched. Sentence 3: To make him lose his composure, his friends decided to trick him. Sentence 4: They invited him to a conference which was in a fact a clown party.
Output:
Charles wasn't happy, but a smile turned the corner of his lips.