
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
Let \( n \) be an integer with \( n \geqslant 2 \). On a slope of a mountain, \( n^{2} \) checkpoints are marked, numbered from 1 to \( n^{2} \) from the bottom to the top. Each of two cable car companies, \( A \) and \( B \), operates \( k \) cable cars numbered from 1 to \( k \); each cable car provides a transfer from some checkpoint to a higher one. For each company, and for any \( i \) and \( j \) with \( 1 \leqslant i < j \leqslant k \), the starting point of car \( j \) is higher than the starting point of car \( i \); similarly, the finishing point of car \( j \) is higher than the finishing point of car \( i \). Say that two checkpoints are linked by some company if one can start from the lower checkpoint and reach the higher one by using one or more cars of that company (no movement on foot is allowed).

Determine the smallest \( k \) for which one can guarantee that there are two checkpoints that are linked by each of the two companies.

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