
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
Grandpa Zhang planted a row of pear trees, with a total of 18 trees, and there is a 3-meter interval between adjacent pear trees. There is a water well next to the first tree. Grandpa Zhang uses a bucket to fetch water from the well, then walks to the trees to water them, using up the water in the bucket and returning to the well to fetch more water. Each tree requires half a bucket of water. After watering the entire row of trees, he rests at his original position. How many meters does Grandpa Zhang need to walk in total during the entire watering process?

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