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
The graph of the rational function $\frac{q(x)}{x^6-4x^5+3x^3+x^2-1} $ has a horizontal asymptote. What is the largest possible degree of $q(x)$?
user
test