
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 a country with 15 cities, some of them are connected by air routes belonging to three airlines. It is known that even if any one of the airlines stops flying, it will still be possible to travel from any city to any other city (possibly with transfers), using the flights of the remaining two airlines. What is the minimum number of air routes that can exist in the country?

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