B"Consider a tree (that is, an undirected connected graph without loops) T_1 and a tree T_2 . Let's define their cartesian product T_1 x T_2 in a following way. Let V be the set of vertices in T_1 and U be the set of vertices in T_2 . Then the set of vertices of graph T_1 x T_2 is V x U , that is, a set of ordered pairs of vertices, where the first vertex in pair is from V and the second -- from U . Let's draw the following edges: Please see the notes section for the pictures of products of trees in the sample tests. Let's examine the graph T_1 x T_2 . How much cycles (not necessarily simple) of length k it contains? Since this number can be very large, print it modulo 998244353 . The sequence of vertices w_1 , w_2 , ..., w_k , where w_i in V x U called cycle, if any neighboring vertices are adjacent and w_1 is adjacent to w_k . Cycles that differ only by the cyclic shift or direction of traversal are still considered different. First line of input contains three integers -- n_1 , n_2 and k ( 2 <= n_1, n_2 <= 4000 , 2 <= k <= 75 ) -- number of vertices in the first tree, number of vertices in the second tree and the cycle length respectively. Then follow n_1 - 1 lines describing the first tree. Each of this lines contains two integers -- v_i, u_i ( 1 <= v_i, u_i <= n_1 ), which define edges of the first tree. Then follow n_2 - 1 lines, which describe the second tree in the same format. It is guaranteed, that given graphs are trees. Print one integer -- number of cycles modulo 998244353 . The following three pictures illustrate graph, which are products of the trees from sample tests. In the first example, the list of cycles of length 2 is as follows: "...