B"You are given a tree (an undirected connected acyclic graph) consisting of n vertices and n - 1 edges. A number is written on each edge, each number is either 0 (let's call such edges 0 -edges) or 1 (those are 1 -edges). Let's call an ordered pair of vertices (x, y) ( x ne y ) valid if, while traversing the simple path from x to y , we never go through a 0 -edge after going through a 1 -edge. Your task is to calculate the number of valid pairs in the tree. The first line contains one integer n ( 2 <= n <= 200000 ) -- the number of vertices in the tree. Then n - 1 lines follow, each denoting an edge of the tree. Each edge is represented by three integers x_i , y_i and c_i ( 1 <= x_i, y_i <= n , 0 <= c_i <= 1 , x_i ne y_i ) -- the vertices connected by this edge and the number written on it, respectively. It is guaranteed that the given edges form a tree. Print one integer -- the number of valid pairs of vertices. The picture corresponding to the first example: "...