In triangle $ABC,$ $\angle A = 90^\circ,$ $AC = 1,$ and $AB = 5.$  Point $D$ lies on ray $\overrightarrow{AC}$ such that $\angle DBC = 2 \angle CBA.$  Compute $AD.$The answer is in the form rac{m}{n}, where gcd(m, n) = 1. Please provide the value of m + n.

Let's think step by step and output the final answer within \boxed{}.
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