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Points:
12 (partial)

Time limit:
0.6s

Memory limit:
32M

Problem type

Allowed languages

Ada, Assembly, Awk, Brain****, C, C#, C++, COBOL, ~~CommonLisp~~, D, Dart, F#, Forth, Fortran, Go, ~~Groovy~~, Haskell, Intercal, Java, JS, Kotlin, Lisp, Lua, ~~Nim~~, ~~ObjC~~, OCaml, ~~Octave~~, Pascal, Perl, PHP, Pike, Prolog, Python, Racket, Ruby, Rust, Scala, Scheme, Sed, Swift, TCL, Text, Turing, VB, Zig

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 .

#### Input Specification

The first line contains two integers, and .

The second line contains integers separated by spaces, the elements of sequence .

#### Output Specification

Output the number of subsequences of whose median is .

#### 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`

#### Explanation for Sample Output 3

In the third example, the four subsequences of with median are , , and .

## Comments

I currently have a O() algorithm in python. Is there a better time complexity in which I can solve it? or is Python just too slow for this problem?

Since , can be in a worst case, which is too slow.