
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 ship was sailing upstream in a river. At 5 PM, the captain noticed that a rubber boat had fallen into the water. The captain immediately ordered to turn the ship around to search for it, and after an hour, they caught up with the rubber boat drifting downstream. Assuming the ship's power remained constant throughout the process, determine the time when the rubber boat was lost.

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