Sky株式会社プログラミングコンテスト2023(AtCoder Beginner Contest 289)
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Problem Statement

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On a number line are person $1$, person $2$, and person $3$. At time $0$, person $1$ is at point $A$, person $2$ is at point $B$, and person $3$ is at point $C$. Here, $A$, $B$, and $C$ are all integers, and $A \equiv B \equiv C \pmod{2}$.

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At time $0$, the three people start random walks. Specifically, a person that is at point $x$ at time $t$ ($t$ is a non-negative integer) moves to point $(x-1)$ or point $(x+1)$ at time $(t+1)$ with equal probability. (All choices of moves are random and independent.)

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Find the probability, modulo $998244353$, that it is at time $T$ that the three people are at the same point for the first time.

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What is rational number modulo $998244353$? We can prove that the sought probability is always a rational number. Moreover, under the Constraints of this problem, when the value is represented as $\frac{P}{Q}$ by two coprime integers $P$ and $Q$, we can prove that there is a unique integer $R$ such that $R \times Q \equiv P\pmod{998244353}$ and $0 \leq R \lt 998244353$. Find such $R$.

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Constraints

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  • $0 \leq A, B, C, T \leq 10^5$
  • $A \equiv B \equiv C \pmod{2}$
  • $A, B, C$, and $T$ 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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A B C T

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Output

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Find the probability, modulo $998244353$, that it is at time $T$ that the three people are at the same point for the first time, and print the answer.

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样例

Input #1
1 1 3 1
Output #1
873463809
The three people are at the same point for the first time at time $1$ with the probability $\frac{1}{8}$. Since $873463809 \times 8 \equiv 1 \pmod{998244353}$, $873463809$ should be printed.
Input #2
0 0 0 0
Output #2
1
The three people may already be at the same point at time $0$.
Input #3
0 2 8 9
Output #3
744570476
Input #4
47717 21993 74147 76720
Output #4
844927176
题目信息

题面与样例版权归 AtCoder 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。