Problem Description

Given a permutation \(a_1, \dots, a_n\) of length \(n\) where each element is between \(1\) and \(n\), find the number of odd-length substrings whose median is \(B\).

• Substring Definition: A substring is obtained by removing some (possibly none) elements from the beginning and/or end of the permutation.

• Median Definition: The median of a sequence is the number that would be in the middle if the sequence were sorted in ascending order.

Input Format

The first line contains two integers \(n\) and \(B\).

The second line contains \(n\) integers, representing a permutation of \(1\) to \(n\).

Output Format

Output the number of odd-length substrings with the median \(B\).

Sample Input and Output

Sample Input #1

5 4
1 2 3 4 5

Sample Output #1

2

Sample Input #2

6 3
1 2 4 5 6 3

Sample Output #2

1

Sample Input #3

7 4
5 7 2 4 3 1 6

Sample Output #3

4

Notes

Sample #3 Explanation

All possible cases: 4, 7 2 4, 5 7 2 4 3, 5 7 2 4 3 1 6.

Data Constraints

For \(100\%\) of the data, \(1 \le n \le 10^5\), \(1 \le B \le n\).

Notes

Translated from COCI2007-2008 CONTEST #1 T5 SREDNJI

见题面 Input 部分

见题面 Output 部分