B"Mitya has a rooted tree with n vertices indexed from 1 to n , where the root has index 1 . Each vertex v initially had an integer number a_v ge 0 written on it. For every vertex v Mitya has computed s_v : the sum of all values written on the vertices on the path from vertex v to the root, as well as h_v -- the depth of vertex v , which denotes the number of vertices on the path from vertex v to the root. Clearly, s_1=a_1 and h_1=1 . Then Mitya erased all numbers a_v , and by accident he also erased all values s_v for vertices with even depth (vertices with even h_v ). Your task is to restore the values a_v for every vertex, or determine that Mitya made a mistake. In case there are multiple ways to restore the values, you're required to find one which minimizes the total sum of values a_v for all vertices in the tree. The first line contains one integer n -- the number of vertices in the tree ( 2 <= n <= 10^5 ). The following line contains integers p_2 , p_3 , ... p_n , where p_i stands for the parent of vertex with index i in the tree ( 1 <= p_i < i ). The last line contains integer values s_1 , s_2 , ..., s_n ( -1 <= s_v <= 10^9 ), where erased values are replaced by -1 . Output one integer -- the minimum total sum of all values a_v in the original tree, or -1 if such tree does not exist. "...