B'You are given a tree, consisting of n vertices. Each edge has an integer value written on it. Let f(v, u) be the number of values that appear exactly once on the edges of a simple path between vertices v and u . Calculate the sum of f(v, u) over all pairs of vertices v and u such that 1 <= v < u <= n . The first line contains a single integer n ( 2 <= n <= 5 cdot 10^5 ) -- the number of vertices in the tree. Each of the next n-1 lines contains three integers v, u and x ( 1 <= v, u, x <= n ) -- the description of an edge: the vertices it connects and the value written on it. The given edges form a tree. Print a single integer -- the sum of f(v, u) over all pairs of vertices v and u such that v < u . '...