
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
Fiona is attending a school reunion with 15 former classmates. At the reunion, there are 6 people who were in her graduating class. She decides to focus on these classmates and tries to guess the nature of the relationships among them. How many pairs of classmates can Fiona observe to guess whether they like or dislike each other?

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