
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
Two athletes start running simultaneously—one from point $A$ to point $B$ and the other from point $B$ to point $A$. They run at different but constant speeds and meet at a distance of 300 meters from point $A$. After reaching points $A$ and $B$, they immediately turn around and meet again at a distance of 400 meters from point $B$. Find the length of the segment $AB$.

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