
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
It takes $P$ physics books and $C$ chemistry books to completely fill a certain shelf, and $C$ is twice the thickness of a physics book. Also, $R$ physics books and $B$ chemistry books would fill this shelf, and $G$ physics books alone would fill the shelf. Express $G$ in terms of $P$ and $C$.

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