
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, B, C, and D need to pass through a dark tunnel using one flashlight. The tunnel is narrow and only allows two people to walk through it at a time. Each time, two people with the flashlight pass through, then one person brings the flashlight back, and this process repeats. If A, B, C, and D take 3, 4, 5, and 6 minutes respectively to pass through the tunnel alone, then the minimum time needed for all four to pass through the tunnel is $\qquad$ minutes.

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