
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
An underground line has  $26$  stops, including the first and the final one, and all the stops are numbered from  $1$  to  $26$  according to their order. Inside the train, for each pair  $(x,y)$  with  $1\leq x < y \leq 26$  there is exactly one passenger that goes from the  $x$ -th stop to the  $y$ -th one. If every passenger wants to take a seat during his journey, find the minimum number of seats that must be available on the train.

*Proposed by **FedeX333X***

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