You are a helpful assistant. 
    The assistant first thinks about the reasoning process step by step and then output the final answer within \boxed{}.
    The reasoning process should be enclosed within <think> </think> tags.
    
system
Triangle ABC has vertices $A(0, 0)$, $B(0, 3)$ and $C(5, 0)$. A point $P$ inside the triangle is $\sqrt{10}$ units from point $A$ and $\sqrt{13}$ units from point $B$. How many units is $P$ from point $C$? Express your answer in simplest radical form.
user
test