AtCoder Beginner Contest 284
G
Only Once
AtCoder
⌀ 2218
原题
← Ex→
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Problem Statement

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For a sequence of length $N$, $A = (A_1,A_2,\dots,A_N)$, consisting of integers between $1$ and $N$, inclusive, and an integer $i\ (1\leq i \leq N)$, let us define a sequence of length $10^{100}$, $B_i=(B_{i,1},B_{i,2},\dots,B_{i,10^{100}})$, as follows.

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  • $B_{i,1}=i$.
  • $B_{i,j+1}=A_{B_{i,j}}\ (1\leq j<10^{100})$.
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Additionally, let us define $S_i$ as the number of distinct integers that occur exactly once in the sequence $B_i$. More formally, $S_i$ is the number of values $k$ such that exactly one index $j\ (1\leq j\leq 10^{100})$ satisfies $B_{i,j}=k$.

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You are given an integer $N$. There are $N^N$ sequences that can be $A$. Find the sum of $\displaystyle \sum_{i=1}^{N} S_i$ over all of them, modulo $M$.

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Constraints

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  • $1\leq N \leq 2\times 10^5$
  • $10^8\leq M \leq 10^9$
  • $N$ and $M$ are integers.
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Input

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The input is given from Standard Input in the following format:

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N M

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Output

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Print the answer as an integer.

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样例

Input #1
4 100000000
Output #1
624
As an example, let us consider the case $A=(2,3,3,4)$. - For $i=1$: we have $B_1=(1,2,3,3,3,\dots)$, where two integers, $1$ and $2$, occur exactly once, so $S_1=2$. - For $i=2$: we have $B_2=(2,3,3,3,\dots)$, where one integer, $2$, occurs exactly once, so $S_2=1$. - For $i=3$: we have $B_3=(3,3,3,\dots)$, where no integers occur exactly once, so $S_3=0$. - For $i=4$: we have $B_4=(4,4,4,\dots)$, where no integers occur exactly once, so $S_4=0$. Thus, we have $\displaystyle \sum_{i=1}^{N} S_i=2+1+0+0=3$. If we similarly compute $\displaystyle \sum_{i=1}^{N} S_i$ for the other $255$ sequences, the sum of this value over all $256$ sequences is $624$.
Input #2
7 1000000000
Output #2
5817084
Input #3
2023 998244353
Output #3
737481389
Print the sum modulo $M$.
Input #4
100000 353442899
Output #4
271798911
题目信息
题号
abc284_g
时间限制
2 s
内存限制
1024 MB

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