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## 문제

You are given integers $A,B$, and a simple undirected graph of $N$ vertices and $M$ edges. The vertices are numbered from $1$ through $N$, and the edges from $1$ through $M$. The edge $i$ connects the vertices $U_i$ and $V_i$. Here, it is guaranteed that $V_i-U_i=A$ or $V_i-U_i=B$.

Find the number of matchings of the graph, modulo $998244353$. Note that a matching of the graph is a subset of edges whose end-points are all distinct.

## 입력

The first line contains integers $N$ ($3 \leq N \leq 200$), $M$ ($1 \leq M \leq 400$), $A$, and $B$ ($1 \leq A < B \leq N-1$).

The following $M$ lines describe the edges. The $i$-th of those lines contains integers $U_i$ and $V_i$ ($1 \leq U_i < V_i \leq N$, $V_i-U_i=A$ or $V_i-U_i=B$). There are no self-loops or multi-edges.

## 출력

Print the answer.

## 예제 입력 1

4 3 1 2
1 2
1 3
3 4


## 예제 출력 1

5


## 예제 입력 2

10 14 2 4
5 7
7 9
2 6
6 8
1 5
3 7
4 8
1 3
4 6
8 10
3 5
5 9
2 4
6 10


## 예제 출력 2

225