
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
$a$, $b$, $c$ are the three sides of triangle $ABC$, let vectors $\overrightarrow{P}=(a+c,b)$, $\overrightarrow{q}=(b-a,c-a)$. If $\overrightarrow{P} \parallel \overrightarrow{q}$, then the size of angle $C$ is \_\_\_\_\_.

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