Let \( f \) be a function from the positive integers to the positive integers such that:
1. \( f \) is increasing, i.e., \( f(n+1) > f(n) \) for all positive integers \( n \),
2. \( f(f(n)) = 2n \) for all positive integers \( n \).

Find \( f(5) \). Let's think step by step and output the final answer within \boxed{}.
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