Score : $500$ points

问题描述

我们有一个长度为 $N$ 的数列 $A = (A_1, A_2, \dots, A_N)$ 和整数 $X$ 与 $Y$。找出满足所有以下条件的整数对 $(L, R)$ 的数量。

• $1 \leq L \leq R \leq N$
• 数列中从第 $L$ 项到第 $R$ 项的最大值是 $X$，最小值是 $Y$。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

We have a number sequence $A = (A_1, A_2, \dots, A_N)$ of length $N$ and integers $X$ and $Y$. Find the number of pairs of integers $(L, R)$ satisfying all the conditions below.

• $1 \leq L \leq R \leq N$
• The maximum value of $A_L, A_{L+1}, \dots, A_R$ is $X$, and the minimum is $Y$.

Constraints

• $1 \leq N \leq 2 \times 10^5$
• $1 \leq A_i \leq 2 \times 10^5$
• $1 \leq Y \leq X \leq 2 \times 10^5$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$N$ $X$ $Y$

$A_1$ $A_2$ $\dots$ $A_N$

Output

Print the answer.

Sample Input 1

4 3 1
1 2 3 1

Sample Output 1

4

$4$ pairs satisfy the conditions: $(L,R)=(1,3),(1,4),(2,4),(3,4)$.

Sample Input 2

5 2 1
1 3 2 4 1

Sample Output 2

0

No pair $(L,R)$ satisfies the condition.

Sample Input 3

5 1 1
1 1 1 1 1

Sample Output 3

15

It may hold that $X=Y$.

Sample Input 4

10 8 1
2 7 1 8 2 8 1 8 2 8

Sample Output 4

36

update @ 2024/3/10 10:35:54