
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 there are two-way non-stopflights between some pairs of cities. Any city can be reached from any other by a sequence of at most  $100$  flights. Moreover, any city can be reached from any other by a sequence of an even number of flights. What is the smallest  $d$  for which one can always claim that any city can be reached from any other by a sequence of an even number of flights not exceeding  $d$ ?

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