Definition: 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, that is, it makes you much less likely to believe the hypothesis is true. A strengthener is a statement that strengthens the hypothesis, that is, it makes you much more likely to believe the hypothesis is true. Your task is to answer with 'strengthener' or 'weakener' if the update strengthens or weakens the hypothesis, respectively.

Positive Example 1 -
Input: Premise: Old man crafting something in his workshop.
Hypothesis: An old man is working.
Update: The man is serious and is surrounded by workers.
Output: strengthener

Positive Example 2 -
Input: Premise: Old man crafting something in his workshop.
Hypothesis: An old man is working.
Update: The man is wearing pajamas and is chuckling.
Output: weakener

Negative Example 1 -
Input: Premise: Old man crafting something in his workshop.
Hypothesis: An old man is working.
Update: The man is serious and is surrounded by workers.
Output: I dont know.

Negative Example 2 -
Input: Premise: Old man crafting something in his workshop.
Hypothesis: An old man is working.
Update: The man is wearing pajamas and is chuckling.
Output: strengthener,weakener.

Now complete the following example -
Input: Premise: A flying machine with a yellow sail is landing with industrial buildings in the background.
Hypothesis: The machine is not gas-operated.
Update: The machine has a battery.
Output: 


Answer: strengthener