
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 one-way trip takes 2 hours and 40 minutes, so a round trip takes 5 hours and 20 minutes. Therefore, after a round trip, a driver must rest for at least one hour.

Let's call the drivers for the first, second, and third trips A, B, and C, respectively. Driver A returns to the station at 12:40. At this time, drivers B and C are still on the route. Driver A cannot start their next trip before 13:40, so there must be a fourth driver D, departing from the station at 13:05.

Four drivers are sufficient. Driver A departs on the fifth trip at 16:10, and driver B, who returns to the station at 16:00, has enough time to rest and departs on the sixth trip at 17:30.

If driver A departs on the 17:30 trip, the 16:10 trip will be without a driver; at this time, driver B has not yet rested, and drivers C and D are still on the route. Consequently, driver A completes the trip from 16:10 to 21:30, bringing Alexey Ivanovich back to the station.

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