AtCoder Grand Contest 069
E
Pair of Sequences
AtCoder
⌀ 4255
原题
← D→
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Problem Statement

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You are given integers $N$, $M$, $X$, and $Y$.

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Find the number, modulo $998244353$, of pairs $(A, B)$ of sequences $A=(a_1,\ldots,a_N)$ and $B=(b_1,\ldots,b_N)$ that satisfy all of the following conditions:

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  • $A = (a_1, \ldots, a_N)$ is a sequence of non-negative integers.
  • $B = (b_1, \ldots, b_N)$ is a subsequence of $(0, 1, \ldots, M - 1)$.
  • $\sum\limits_{i=1}^{N} a_i = X$.
  • $\sum\limits_{i=1}^{N} a_i b_i = Y$.
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Constraints

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  • $1 \leq N \leq M \leq 2 \times 10^5$
  • $1 \leq X, Y \leq 2 \times 10^5$
  • All input values 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 X Y

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Output

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Print the answer modulo $998244353$.

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样例

Input #1
3 4 3 4
Output #1
5
Here are the five pairs $(A, B)$ satisfying the conditions: - $A = (0, 2, 1)$, $B = (0, 1, 2)$ - $A = (1, 0, 2)$, $B = (0, 1, 2)$ - $A = (1, 1, 1)$, $B = (0, 1, 3)$ - $A = (1, 2, 0)$, $B = (0, 2, 3)$ - $A = (2, 1, 0)$, $B = (1, 2, 3)$
Input #2
1 1 1 1
Output #2
0
There are no pairs $(A, B)$ satisfying the conditions.
Input #3
12345 67890 9876 54321
Output #3
150392014
Find the count modulo $998244353$.
题目信息
题号
agc069_e
时间限制
8 s
内存限制
2048 MB

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