B'Given a tree with n nodes numbered from 1 to n . Each node i has an associated value V_i . If the simple path from u_1 to u_m consists of m nodes namely u_1 rightarrow u_2 rightarrow u_3 rightarrow ... u_{m-1} rightarrow u_{m} , then its alternating function A(u_{1},u_{m}) is defined as A(u_{1},u_{m}) = sum limits_{i=1}^{m} (-1)^{i+1} cdot V_{u_{i}} . A path can also have 0 edges, i.e. u_{1}=u_{m} . Compute the sum of alternating functions of all unique simple paths. Note that the paths are directed: two paths are considered different if the starting vertices differ or the ending vertices differ. The answer may be large so compute it modulo 10^{9}+7 . The first line contains an integer n (2 <= q n <= q 2 cdot10^{5} ) -- the number of vertices in the tree. The second line contains n space-separated integers V_1, V_2, ldots, V_n ( -10^9 <= q V_i <= q 10^9 ) -- values of the nodes. The next n-1 lines each contain two space-separated integers u and v (1 <= q u, v <= q xe2 x80 x89n, u neq v) denoting an edge between vertices u and v . It is guaranteed that the given graph is a tree. Print the total sum of alternating functions of all unique simple paths modulo 10^{9}+7 . Consider the first example. A simple path from node 1 to node 2 : 1 rightarrow 2 has alternating function equal to A(1,2) = 1 cdot (-4)+(-1) cdot 1 = -5 . A simple path from node 1 to node 3 : 1 rightarrow 3 has alternating function equal to A(1,3) = 1 cdot (-4)+(-1) cdot 5 = -9 . A simple path from node 2 to node 4 : 2 rightarrow 1 rightarrow 4 has alternating function A(2,4) = 1 cdot (1)+(-1) cdot (-4)+1 cdot (-2) = 3 . A simple path from node 1 to node 1 has a single node 1 , so A(1,1) = 1 cdot (-4) = -4 . Similarly, A(2, 1) = 5 , A(3, 1) ='...