
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 map of a park where Dave, Emily, and Fiona are at can be depicted by the Cartesian plane. Dave is located at $(8, -15)$ and Emily is at $(4, 18)$. They decide to meet at the midpoint between their locations and then move horizontally to reach Fiona, whose location is at $\left(5, \frac{18+(-15)}{2}\right)$. What is the horizontal distance (in units) Dave and Emily need to travel together to reach Fiona?

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