
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
Given three different prime numbers \( p, q, r \) such that \( pqr = 1899\ldots962 \) (where the number contains \( n \) nines), define \( f(n) \) as the sum of the digits of the natural number \( n \). Determine the value of \( f(p) + f(q) + f(r) - f(pqr) \).

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