
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 that exchanging any two letters in an algebraic expression does not change the expression, determine which expressions among $a(b+c)+b(a+c)+c(a+b)$, $a^2bc+b^2ac+c^2ab$, and $a^2+b^2+c^2-ab-bc-ac$ are completely symmetric expressions.

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