In this task, you are given a premise, a hypothesis, and an update. The premise sentence describes a real-world situation and is always assumed to be true. The hypothesis sentence describes an assumption or inference that you might make about that situation having read the premise. The update provides additional information about the situation that might weaken or strengthen the hypothesis. A weakener is a statement that weakens the hypothesis. It makes you much less likely to believe the hypothesis is true. A strengthener is a statement that strengthens the hypothesis. It makes you much more likely to believe the hypothesis is true. Your task is to output 'strengthener' or 'weakener' if the update strengths or weakens the hypothesis, respectively.

Let me give you an example: Premise: PersonX seems interested
Hypothesis: PersonX then good activity
Update: PersonX was a good student
The answer to this example can be: strengthener
Here is why: If PersonX was a good student, it is more likely that PersonX would do good activities.

OK. solve this:
Premise: PersonX receives a letter
Hypothesis: As a result, PersonX feels social
Update: The letter was a Christmas letter.
Answer:
strengthener