Codeforces Round 842 (Div. 2)
E
Partial Sorting
Codeforces
2300
原题
← DF →
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Consider a permutation$^\dagger$ $p$ of length $3n$. Each time you can do one of the following operations:

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  • Sort the first $2n$ elements in increasing order.
  • Sort the last $2n$ elements in increasing order.
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We can show that every permutation can be made sorted in increasing order using only these operations. Let's call $f(p)$ the minimum number of these operations needed to make the permutation $p$ sorted in increasing order.

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Given $n$, find the sum of $f(p)$ over all $(3n)!$ permutations $p$ of size $3n$.

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Since the answer could be very large, output it modulo a prime $M$.

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$^\dagger$ A permutation of length $n$ is an array consisting of $n$ distinct integers from $1$ to $n$ in arbitrary order. For example, $[2,3,1,5,4]$ is a permutation, but $[1,2,2]$ is not a permutation ($2$ appears twice in the array), and $[1,3,4]$ is also not a permutation ($n=3$ but there is $4$ in the array).

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Input

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The only line of input contains two numbers $n$ and $M$ ($1 \leq n \leq 10^6$, $10^8 \leq M \leq 10^9$). It is guaranteed that $M$ is a prime number.

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Output

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Output the answer modulo $M$.

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Note

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In the first test case, all the permutations are:

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  • $[1, 2, 3]$, which requires $0$ operations;
  • $[1, 3, 2]$, which requires $1$ operation;
  • $[2, 1, 3]$, which requires $1$ operation;
  • $[2, 3, 1]$, which requires $2$ operations;
  • $[3, 1, 2]$, which requires $2$ operations;
  • $[3, 2, 1]$, which requires $3$ operations.
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Therefore, the answer is $0+1+1+2+2+3=9$.

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样例

Input #1
1 100009067
Output #1
9
InputCopy OutputCopy
Input #2
2 100000357
Output #2
1689
InputCopy OutputCopy
Input #3
69 999900997
Output #3
193862705
InputCopy OutputCopy
题目信息
题号
1768E
时间限制
1.5 s
内存限制
1024 MB
标签
组合数学
数学
数论

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