see tutorial about stern-brocot's tree [Tutorial](https://en.wikipedia.org/wiki/Stern%E2%80%93Brocot_tree). this is infinity binary tree which nodes are irreducible fractions. enumerate nodes of tree using BFS. it is given one number n and one fraction $\frac{a}{b}$. Your task is to determine what fraction is written on the node LCA($n$, $\frac{a}{b}$) where LCA is Lowest Common Ancestor of nodes n and $\frac{a}{b}$. (in first case node is defined by its number and in second case node is defined by fraction). $0<a,b<10^9$ and $0<n<10^18$. ↵
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what is efficient method for finding what fraction is written on the node by its fraction and vice versa?↵
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what is efficient method for finding what fraction is written on the node by its fraction and vice versa?↵
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