题目描述
Problem Statement
In the following undirected graph, count the number of walks from S to S that pass through the edges ST, TU, UV, VS (in any direction) exactly a, b, c, d times, respectively, modulo 998,244,353.
Input
Input is given from Standard Input in the following format:
a b c d
Output
Print the answer.
Constraints
- $1 \leq a, b, c, d \leq 500,000$
- All values in the input are integers.
Sample Input 1
2 2 2 2
Sample Output 1
10
There are 10 walks that satisfy the condition.
One example of such a walk is
$S \rightarrow T \rightarrow U \rightarrow V \rightarrow U \rightarrow T \rightarrow S \rightarrow V \rightarrow S$.
Sample Input 2
1 2 3 4
Sample Output 2
0
Sample Input 3
470000 480000 490000 500000
Sample Output 3
712808431
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
2 2 2 2
样例输出
10