
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
Mr. Zhang and Mr. Wang, each with their spouse and one child, went to a zoo together. After purchasing tickets, they lined up to enter the zoo. For safety reasons, the two fathers had to be at the front and back of the line, respectively, and the two children had to be next to each other. The total number of different ways they could line up to enter the zoo is ______.

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