Technocup 2022 - Elimination Round 3
F
Non-equal Neighbours
Codeforces
2400
原题
← EG →
翻译中…

You are given an array of $n$ positive integers $a_1, a_2, \ldots, a_n$. Your task is to calculate the number of arrays of $n$ positive integers $b_1, b_2, \ldots, b_n$ such that:

翻译中…
  • $1 \le b_i \le a_i$ for every $i$ ($1 \le i \le n$), and
  • $b_i \neq b_{i+1}$ for every $i$ ($1 \le i \le n - 1$).
翻译中…

The number of such arrays can be very large, so print it modulo $998\,244\,353$.

翻译中…

Input

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The first line contains a single integer $n$ ($1 \le n \le 2 \cdot 10^5$) — the length of the array $a$.

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The second line contains $n$ integers $a_1, a_2, \ldots, a_n$ ($1 \le a_i \le 10^9$).

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Output

翻译中…

Print the answer modulo $998\,244\,353$ in a single line.

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Note

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In the first test case possible arrays are $[1, 2, 1]$ and $[2, 1, 2]$.

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In the second test case possible arrays are $[1, 2]$, $[1, 3]$, $[2, 1]$ and $[2, 3]$.

翻译中…

样例

Input #1
3
2 2 2
Output #1
2
InputCopy OutputCopy
Input #2
2
2 3
Output #2
4
InputCopy OutputCopy
Input #3
3
1 1 1
Output #3
0
InputCopy OutputCopy
题目信息
题号
1585F
时间限制
3 s
内存限制
512 MB
标签
组合数学
动态规划
数学

题面与样例版权归 Codeforces 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。