
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 classified area is a rectangle of $200 \times 300$ meters. There is one guard at each of the four corners outside the area. An intruder approaches the perimeter of the classified area from the outside, and all the guards run to the intruder by the shortest routes along the outside perimeter (the intruder remains stationary). The total distance covered by three of the guards to reach the intruder is 850 meters. How many meters did the fourth guard run to reach the intruder?

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