utils/scrapers/prescraped/codeforces/Problems/1981F

Note the unusual definition of $$$\text{MEX}$$$ in this problem.Piggy gave Turtle a binary tree$$$^{\dagger}$$$ with $$$n$$$ vertices and a sequence $$$a_1, a_2, \ldots, a_n$$$ on his birthday. The binary tree is rooted at vertex $$$1$$$.If a set of paths $$$P = \{(x_i, y_i)\}$$$ in the tree covers each edge exactly once, then Turtle will think that the set of paths is good. Note that a good set of paths can cover a vertex twice or more.Turtle defines the value of a set of paths as $$$\sum\limits_{(x, y) \in P} f(x, y)$$$, where $$$f(x, y)$$$ denotes the $$$\text{MEX}^{\ddagger}$$$ of all $$$a_u$$$ such that vertex $$$u$$$ is on the simple path from $$$x$$$ to $$$y$$$ in the tree (including the starting vertex $$$x$$$ and the ending vertex $$$y$$$).Turtle wonders the minimum value over all good sets of paths. Please help him calculate the answer!$$$^{\dagger}$$$A binary tree is a tree where every non-leaf vertex has at most $$$2$$$ sons.$$$^{\ddagger}\text{MEX}$$$ of a collection of integers $$$c_1, c_2, \ldots, c_k$$$ is defined as the smallest positive integer $$$x$$$ which does not occur in the collection $$$c$$$. For example, $$$\text{MEX}$$$ of $$$[3, 3, 1, 4]$$$ is $$$2$$$, $$$\text{MEX}$$$ of $$$[2, 3]$$$ is $$$1$$$.