The function $f(n)$ satisfies $f(1) = 1$ and $f(2n + 1) = f(n) + 1$ for $n \ge 0.$  Find $f(15).$
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
The function $f(n)$ satisfies $f(1) = 1$ and $f(2n + 1) = f(n) + 1$ for $n \ge 0.$  Find $f(15).$
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
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The function $f(n)$ satisfies $f(1) = 1$ and $f(2n + 1) = f(n) + 1$ for $n \ge 0.$  Find $f(15).$
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