
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 triangle \(ABC\), \(AC = 18 \, \text{cm}\) and \(BC = 21 \, \text{cm}\). Point \(K\) is the midpoint of side \(BC\), and point \(M\) is the midpoint of side \(AB\). Point \(N\) lies on side \(AC\) such that \(AN = 6 \, \text{cm}\). Additionally, \(MN = KN\). Find the length of side \(AB\).

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