Technocup 2022 - Elimination Round 3
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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$i$($1 \le i \le n - 1$).
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The number of such arrays can be very large, so print it modulo $998\,244\,353$.
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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
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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 $[2, 3]$.
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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
标签
组合数学
动态规划
数学
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