时间限制：C/C++/Rust/Pascal 1秒，其他语言2秒
空间限制：C/C++/Rust/Pascal 256 M，其他语言512 M
64bit IO Format: %lld
空间限制：C/C++/Rust/Pascal 256 M，其他语言512 M
64bit IO Format: %lld
题目描述
It is not hard to see the answer to this problem is P-recursive.
The number of inversion pairs of a permutation 
is the number of pairs 
such that 
and 
.
You are asked to calculate the sum of the k-th power of the inversion pairs of all permutations with length
.
The answer can be large, output it modulo
You are asked to calculate the sum of the k-th power of the inversion pairs of all permutations with length
The answer can be large, output it modulo
输入描述:
The first line contains two integers.
输出描述:
Output one integer - the answer.