
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
A kingdom's road map is given. Cities are represented by numbers, and the segments represent roads. Once, a wandering knight started his journey in one of the kingdom's cities and managed to build his route to travel each road exactly once. At which numbered city could he have started his route? Indicate all possible options.

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