AtCoder Beginner Contest 281
Ex
Alchemy
AtCoder
⌀ 3180
原题
←G →
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Problem Statement

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Takahashi has $A$ kinds of level-$1$ gems, and $10^{10^{100}}$ gems of each of those kinds. For an integer $n$ greater than or equal to $2$, he can put $n$ gems that satisfy all of the following conditions into a cauldron to generate a level-$n$ gem in return.

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  • No two gems are of the same kind.
  • Every gem's level is less than $n$.
  • For every integer $x$ greater than or equal to $2$, there is at most one level-$x$ gem.
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Find the number of kinds of level-$N$ gems that Takahashi can obtain, modulo $998244353$.

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Here, two level-$2$ or higher gems are considered to be of the same kind if and only if they are generated from the same set of gems.

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  • Two sets of gems are distinguished if and only if there is a gem in one of those sets such that the other set does not contain a gem of the same kind.
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Any level-$1$ gem and any level-$2$ or higher gem are of different kinds.

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Constraints

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  • $1 \leq N \leq 2 \times 10^5$
  • $1 \leq A \leq 10^9$
  • $N$ and $A$ 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 A

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Output

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Print the answer.

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样例

Input #1
3 3
Output #1
10
Here are ten ways to obtain a level-$3$ gem. - Put three kinds of level-$1$ gems into the cauldron. - Takahashi has three kinds of level-$1$ gems, so there is one way to choose three kinds of level-$1$ gems. Thus, he can obtain one kind of level-$3$ gem in this way. - Put one kind of level-$2$ gem and two kinds of level-$1$ gems into the cauldron. - A level-$2$ gem can be obtained by putting two kinds of level-$1$ gems into the cauldron. - Takahashi has three kinds of level-$1$ gems, so there are three ways to choose two kinds of level-$1$ gems. Thus, three kinds of level-$2$ gems are available here. - There are three kinds of level-$2$ gems, and three ways to choose two kinds of level-$1$ gems, so he can obtain $3 \times 3 = 9$ kinds of level-$3$ gems in this way.
Input #2
1 100
Output #2
100
Input #3
200000 1000000000
Output #3
797585162
题目信息
题号
abc281_h
时间限制
4 s
内存限制
1024 MB

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