
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
Among the following groups, M and P represent the same set in \_\_\_\_\_\_ (fill in the serial number).  
①M={3, -1}, P={(3, -1)};  
②M={(3, 1)}, P={(1, 3)};  
③M={y|y=x^2-1, x∈R}, P={a|a=x^2-1, x∈R};  
④M={y|y=x^2-1, x∈R}, P={(x, y)|y=x^2-1, x∈R}.

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