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
How many congruent 4-foot tall cylindrical pipes with an inside diameter of 2 inches are needed to hold the same amount of water as one pipe of the same height with an inside diameter of 12 inches?
user
test