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
Two sides of a triangle have lengths of 18 and 29 units. If the third side has an integer length, what is the positive difference between the maximum and minimum length of the third side?
user
test