Consider a sequence of integers, containing integers between and . Each integer appears exactly once in the sequence.
A subsequence of is a sequence obtained by removing some (possibly none) numbers from the beginning of , and then from the end of . Calculate how many different subsequences of of odd length have their median equal to . The median of a sequence is the element in the middle of the sequence after it is sorted. For example, the median of the sequence is .
The first line contains two integers, and .
The second line contains integers separated by spaces, the elements of sequence .
Output the number of subsequences of whose median is .
Sample Input 1
5 4 1 2 3 4 5
Sample Output 1
Sample Input 2
6 3 1 2 4 5 6 3
Sample Output 2
Sample Input 3
7 4 5 7 2 4 3 1 6
Sample Output 3
Explanation for Sample Output 3
In the third example, the four subsequences of with median are , , and .