Home

Problem Statement

Given are a tree with $N$ vertices, a sequence of $M$ numbers $A=(A_1,\ldots,A_M)$, and an integer $K$.
The vertices are numbered $1$ through $N$, and the $i$-th edge connects Vertices $U_i$ and $V_i$.

We will paint each of the $N-1$ edges of this tree red or blue. Among the $2^{N-1}$ such ways, find the number of ones that satisfies the following condition, modulo $998244353$.

Condition:
Let us put a piece on Vertex $A_1$, and for each $i=1,\ldots,M-1$ in this order, move it from Vertex $A_i$ to Vertex $A_{i+1}$ along the edges in the shortest path. After all of these movements, $R-B=K$ holds, where $R$ and $B$ are the numbers of times the piece traverses a red edge and a blue edge, respectively.

Constraints

• $2 \leq N \leq 1000$
• $2 \leq M \leq 100$
• $|K| \leq 10^5$
• $1 \leq A_i \leq N$
• $1\leq U_i,V_i\leq N$
• The given graph is a tree.
• All values in input are integers.

Sample Input 1

4 5 0
2 3 2 1 4
1 2
2 3
3 4

Sample Output 1

2

If we paint the $1$-st and $3$-rd edges red and the $2$-nd edge blue, the piece will traverse the following numbers of red and blue edges:

• $0$ red edges and $1$ blue edge when moving from Vertex $2$ to $3$,
• $0$ red edges and $1$ blue edge when moving from Vertex $3$ to $2$,
• $1$ red edge and $0$ blue edges when moving from Vertex $2$ to $1$,
• $2$ red edges and $1$ blue edge when moving from Vertex $1$ to $4$,

for a total of $3$ red edges and $3$ blue edges, satisfying the condition.

Another way to satisfy the condition is to paint the $1$-st and $3$-rd edges blue and the $2$-nd edge red. There is no other way to satisfy it, so the answer is $2$.

Sample Input 2

3 10 10000
1 2 1 2 1 2 2 1 1 2
1 2
1 3

Sample Output 2

0

There may be no way to paint the tree to satisfy the condition.

Sample Input 3

10 2 -1
1 10
1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10

Sample Output 3

126

Sample Input 4

5 8 -1
1 4 1 4 2 1 3 5
1 2
4 1
3 1
1 5

Sample Output 4

2