
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
In a certain agency, there are 18 elderly, 12 middle-aged, and 6 young people. Now, a sample of size $X$ is drawn. If systematic sampling and stratified sampling are used, no individuals need to be removed. However, if the sample size is increased by 1, and systematic sampling is used, 1 individual needs to be removed from the population. Then, the sample size $X$ is $\boxed{\_\_\_\_\_\_\_\_}$.

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