
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
For a proposition $p$: "If two lines $l_1: a_1x + b_1y + c_1 = 0$ and $l_2: a_2x + b_2y + c_2 = 0$ are parallel, then $a_1b_2 - a_2b_1 = 0$." Let $f(p)$ denote the number of true propositions among the four forms of proposition $p$ (the original proposition, the converse, the negation, and the contrapositive). Find $f(p)$.

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