
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
Islandland consists of ten islands, some of which are connected by two-way air routes. If you select any 9 islands, it is possible to fly around them one by one and return to the starting island. Find the minimum number of air routes that can exist in this country.

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