Let $a$ and $b$ be positive integers satisfying $\frac{ab+1}{a+b} < \frac{3}{2}$. Find the maximum possible value of $\frac{a^3b^3+1}{a^3+b^3}.$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Let $a$ and $b$ be positive integers satisfying $\frac{ab+1}{a+b} < \frac{3}{2}$. Find the maximum possible value of $\frac{a^3b^3+1}{a^3+b^3}.$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
\frac{31}{5}
Let $a$ and $b$ be positive integers satisfying $\frac{ab+1}{a+b} < \frac{3}{2}$. Find the maximum possible value of $\frac{a^3b^3+1}{a^3+b^3}.$
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