
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
Let $f(x)$ be an increasing function defined on $\mathbb{R}$, and for any $x$, it always holds that $f(-x) + f(x) = 0$. If the real numbers $m$ and $n$ satisfy the inequality $f(m^2-6m+21) + f(n^2-8n) < 0$, then the range of values for $m^2+n^2$ is.

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