Better Together Twice

Problem Statement

In an array A containing N elements, each element is initially assigned its own value. Over time, the values evolve such that non$-$zero elements increase the value of their adjacent elements by $2$ each day. Specifically, if the $\backslash ($ i $\backslash )-$th element holds a non$-$zero value, both the $(\backslash ($ i$-1\backslash ))-$th and $(\backslash ($ i$+1\backslash ))-$th elements $($if they exist$)$ increase by $2.$

The initial day is designated as day $0,$ with subsequent days denoted as day $1,$ day $2,$ and so forth. The task is to compute the difference between the additon of values of all elements on day $\backslash ($ P $\backslash )$ and additon of values of all elements on day $0.$

Input Format

First line contains two integers N and P representing size of array and the Pth day.

Second line contains N integers value of each element on day $0.$

Output Format

A single integer representing the difference in the total sum of all elements between day $\backslash ($ P $\backslash )$ and day $0.$

Constraints

$\backslash [$

$\backslash$begin$\{$array$\}\{$l$\}$

N$,$ F

A$[$i

$\backslash$end$\{$array$\}$

$\backslash ]$

Sample Testcase $1$

Testcase Input

$17$

$10$

Testcase Output