题目描述
Problem Description
Consider integers between $1$ and $2N$. Snuke wants to divide these integers into $N$ pairs satisfying the following conditions:
- Each integer between $1$ and $2N$ is included in exactly one pair.
- There are exactly $A$ pairs with a difference of $1$.
- There are exactly $B$ pairs with a difference of $2$.
- There are exactly $C$ pairs with a difference of $3$.
Due to the constraints, it is guaranteed that $N = A + B + C$, so there are no pairs with a difference of $4$ or more.
Find the number of ways to divide these pairs, modulo $10^9+7$.
Input Format
The input is given from the standard input in the following format:
$ N $ $ A $ $ B $ $ C $
Output Format
Output the answer.
Sample Input and Output
Sample Input #1
3 1 2 0
Sample Output #1
2
Sample Input #2
600 100 200 300
Sample Output #2
522158867
Notes/Hints
Constraints
- $1 \leq N \leq 5000$
- $0 \leq A, B, C$
- $ A + B + C = N $
Sample Explanation 1
There are two ways: $1-2, 3-5, 4-6$ and $1-3, 2-4, 5-6$.
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分
样例输入
3 1 2 0
样例输出
2