A robot on Mars is trying to help an astronaut reach the base station $15$ kilometers away. The

robot has limited fuel, and it must find the most efficient way to travel to the base. The goal is to

help the astronaut reach the base while saving fuel.

The robot can do these actions:

$$ Move forward some distance, which uses fuel.

$$ Drop extra fuel at a specific location to use later.

$$ Refill fuel from a location where it has dropped fuel earlier.

Robot's rules:

$$ The robot starts with $3$ fuel capsules.

$$ Each fuel capsule lets the robot move up to $9$ kilometers.

$$ If the robot runs out of fuel, it must return to where it dropped extra fuel to refuel.