
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
Billy has 15 boxes. Nine of the boxes contain crayons, six of the boxes contain markers, and four of the boxes contain both crayons and markers. How many boxes contain neither crayons nor markers?

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