
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
A person wants to buy a house. As the floor level increases, the energy consumed in going up and down the stairs increases, leading to higher dissatisfaction. When living on the $n$th floor, the dissatisfaction caused by going up and down the stairs is $n$. However, the higher floors have fresher air, less noise, and a quieter environment, leading to a decrease in dissatisfaction with the environment as the floor level increases. It is given that when living on the $n$th floor, the dissatisfaction level with the environment is $\frac{9}{n}$. Therefore, the person should choose the ______ floor to achieve the highest satisfaction level.

Present the answer in LaTex format: \boxed{Your answer}
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