
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 the arithmetic sequence $\{a_n\}$, $a_1 > 0$, $a_{10}a_{11} < 0$, if the sum of the first 10 terms of this sequence is $S_{10} = p$, and the sum of the first 18 terms is $S_{18} = q$, then the sum of the first 18 terms of the sequence $\{|a_n|\}$ is $T_{18} =$ .

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