
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 fisherman caught 30 fish from a pond, marked them, and then released them back into the pond, allowing the marked fish to mix thoroughly with the rest of the fish. Ten days later, he caught 50 fish from the pond and found that 2 of them were marked. Based on this, it is estimated that there are approximately ______ fish in the pond.

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