
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
There are four individuals, A, B, C, and D, who need to cross a bridge from the left side to the right side at night. The bridge can only accommodate two people at a time, and there's only one flashlight available, which must be used to cross the bridge. The fastest times each individual takes to cross the bridge are as follows: A takes 2 minutes; B takes 3 minutes; C takes 8 minutes; D takes 10 minutes. As the quicker person must wait for the slower one, the task is to get all four across the bridge in 21 minutes or less. The first to cross the bridge are A and B together, then ____ returns alone. After coming back, the flashlight is passed to ____ and ____, who cross together. Once they reach the other side, they hand the flashlight to ____, who brings it back. Finally, A and B cross the bridge together again.

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