
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 is required to make a box with a square base for placing boxes that are 9 cm wide and 21 cm long. What should be the minimum length of the side of the square base so that the boxes fit in the box snugly?

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