
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
In November 2014, Beijing successfully hosted the 22nd Informal Leaders' Meeting of the Asia-Pacific Economic Cooperation (APEC), attended by leaders or representatives from 21 countries and regions. The organizing committee arranged for these 21 leaders or representatives to take a group photo in two rows, with 11 people in the front row and 10 in the back. The Chinese leader stood in the middle of the front row, with leaders from the United States and Russia standing on either side. If no requirements are imposed on the positions of the other leaders or representatives, how many different arrangements are there in total (expressed in terms of permutations and combinations)?

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