write a go solution for Description:
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_1xT_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_1xT_2 is VxU, 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:

- Between (v,u_1) and (v,u_2) there is an undirected edge, if u_1 and u_2 are adjacent in U.
- Similarly, between (v_1,u) and (v_2,u) there is an undirected edge, if v_1 and v_2 are adjacent in V.

Please see the notes section for the pictures of products of trees in the sample tests.

Let's examine the graph T_1xT_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_iinVxU 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.

Input Format:
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.

Output Format:
Print one integer — number of cycles modulo 998244353.

Note:
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:

- «AB», «BA»
- «BC», «CB»
- «AD», «DA»
- «CD», «DC». Output only the code with no comments, explanation, or additional text.