题目描述
Problem Statement
You are given an even number N and a prime number M.
Find the number, modulo M, of simple connected undirected graphs G with N vertices numbered 1 to N that satisfy the following condition:
- For every spanning tree T of G, there is a perfect matching in T.
What is a perfect matching in a graph?
For a graph G, a set of edges E from G is called a perfect matching in G if, for every vertex v in the graph, E contains exactly one edge with v as an endpoint.
Input
The input is given from Standard Input in the following format:
N M
Output
Print the answer.
Constraints
- $2 \leq N \leq 500$
- $10^8 \leq M \leq 10^9$
- N is even.
- M is prime.
- All input values are integers.
Sample Input 1
4 998244353
Sample Output 1
15
For example, among the two graphs shown in the figure below, the graph on the left satisfies the condition. On the other hand, the graph on the right does not because there is no perfect matching in the spanning tree with the three edges shown in bold red.
Sample Input 2
10 998244353
Sample Output 2
128792160
Sample Input 3
300 923223991
Sample Output 3
359143490
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分