
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 certain high school has a total of 1800 students, among which there are 600 students in the second year of high school. Now, using stratified sampling, $n$ students are selected from the entire school, including 21 students from the second year. Find $n$.

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