AtCoder Regular Contest 176 (Sponsored by Mynavi)
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Problem Statement
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There is a tree with $NM+1$ vertices numbered $0$ to $NM$. The $i$-th edge ($1 \le i \le NM$) connects vertices $i$ and $\max(i-N,0)$.
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Initially, vertex $i$ is colored with color $i \bmod N$. You can perform the following operation zero or more times:
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- Choose two vertices
$u$and$v$connected by an edge. Repaint the color of vertex$u$with that of vertex$v$.
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Find the number, modulo $998244353$, of possible trees after the operations. Two trees are distinguished if and only if some vertex has different colors.
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Constraints
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$1 \le N, M \le 2 \times 10^5$
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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.
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样例
Input #1
3 1
Output #1
42
One possible sequence of operations is as follows. Including this one, there are $42$ possible final trees.

Input #2
4 2
Output #2
219100
Input #3
20 24
Output #3
984288778
Input #4
123456 112233
Output #4
764098676
题目信息
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