
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
If swapping any two letters in an algebraic expression does not change the expression, then this expression is called a completely symmetric expression, such as $a+b+c$ is a completely symmetric expression. Among the following three algebraic expressions: (1) $(a-b)^2$ (2) $ab+bc+ca$ (3) $a^2b+b^2c+c^2a$, the completely symmetric expressions are (fill in the serial numbers).

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