AtCoder Beginner Contest 297
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Problem Statement
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A positive-integer sequence is said to be splendid if no two adjacent elements are equal.
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Find the sum, modulo $998244353$, of the lengths of all splendid sequences whose elements have a sum of $N$.
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Constraints
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$1 \le N \le 2 \times 10^5$- All values in the input 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翻译中…
Output
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Print the answer.
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样例
Input #1
4
Output #1
8
There are four splendid sequences whose sum is $4$: $(4),(1,3),(3,1),(1,2,1)$. Thus, the answer is the sum of their lengths: $1+2+2+3=8$.
$(2,2)$ and $(1,1,2)$ also have a sum of $4$ but ineligible because their $1$-st and $2$-nd elements are the same.
Input #2
297
Output #2
475867236
Input #3
123456
Output #3
771773807
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。