E - LEQ and NEQ /

### 問題文

• 1 \leq X_i \leq A_i
• X_i \neq X_{i+1} (1 \leq i \leq N-1)

### 制約

• 2 \leq N \leq 5 \times 10^5
• 1 \leq A_i \leq 10^9

### 入力

N
A_1 A_2 \ldots A_N


### 入力例 1

3
2 3 2


### 出力例 1

6


• 1,2,1
• 1,3,1
• 1,3,2
• 2,1,2
• 2,3,1
• 2,3,2

### 入力例 2

10
158260522 877914575 602436426 24979445 861648772 623690081 433933447 476190629 262703497 211047202


### 出力例 2

524691026


Score : 700 points

### Problem Statement

Given is a sequence of N integers A_1,A_2,\ldots,A_N. Print the number, modulo 998244353, of sequences of N integers X_1,X_2,\ldots,X_N satisfying all of the following conditions:

• 1 \leq X_i \leq A_i
• X_i \neq X_{i+1} (1 \leq i \leq N-1)

### Constraints

• 2 \leq N \leq 5 \times 10^5
• 1 \leq A_i \leq 10^9

### Input

Input is given from Standard Input in the following format:

N
A_1 A_2 \ldots A_N


### Sample Input 1

3
2 3 2


### Sample Output 1

6


The following six sequences satisfy all of the conditions.

• 1,2,1
• 1,3,1
• 1,3,2
• 2,1,2
• 2,3,1
• 2,3,2

### Sample Input 2

10
158260522 877914575 602436426 24979445 861648772 623690081 433933447 476190629 262703497 211047202


### Sample Output 2

524691026