Find the smallest number $y$ such that $y^2 = 81$.
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Find the smallest number $y$ such that $y^2 = 81$.
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
-9
Find the smallest number $y$ such that $y^2 = 81$.
train