CF1585F.Non-equal Neighbours

普及/提高-

通过率：0%

AC君温馨提醒

该题目为【codeforces】题库的题目，您提交的代码将被提交至codeforces进行远程评测，并由ACGO抓取测评结果后进行展示。由于远程测评的测评机由其他平台提供，我们无法保证该服务的稳定性，若提交后无反应，请等待一段时间后再进行重试。

题目描述

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:

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

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

输入格式

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

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

输出格式

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

输入输出样例

输入#1
```
3
2 2 2
```
输出#1
```
2
```
输入#2
```
2
2 3
```
输出#2
```
4
```
输入#3
```
3
1 1 1
```
输出#3
```
0
```

说明/提示

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

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

首页