Problem:
Score : 300 points

Problem Statement

There are N candles placed on a number line.
The i-th candle from the left is placed on coordinate x_i.
Here, x_1 < x_2 < ... < x_N holds.

Initially, no candles are burning.
Snuke decides to light K of the N candles.

Now, he is at coordinate 0.
He can move left and right along the line with speed 1.
He can also light a candle when he is at the same position as the candle, in negligible time.

Find the minimum time required to light K candles.

Constraints

1 \leq N \leq 10^5

1 \leq K \leq N

x_i is an integer.

|x_i| \leq 10^8

x_1 < x_2 < ... < x_N

Input

Input is given from Standard Input in the following format:

N K
x_1 x_2 ... x_N

Output

Print the minimum time required to light K candles.

Sample Input 1

5 3
-30 -10 10 20 50

Sample Output 1

40

He should move and light candles as follows:

Move from coordinate 0 to -10.

Light the second candle from the left.

Move from coordinate -10 to 10.

Light the third candle from the left.

Move from coordinate 10 to 20.

Light the fourth candle from the left.

Sample Input 2

3 2
10 20 30

Sample Output 2

20

Sample Input 3

1 1
0

Sample Output 3

0

There may be a candle placed at coordinate 0.

Sample Input 4

8 5
-9 -7 -4 -3 1 2 3 4

Sample Output 4

10

Solution in PHP (5.6.30) (judge verdict: Wrong Answer)

<?php 
fscanf(STDIN, "%d %d",$N, $K);
$input=explode(' ',trim(fgets(STDIN)));

for($i=0;$i<$N;$i++){
 $input[$i]=abs($input[$i]); 
}
sort($input);
$current_pos = 0;
$current_num=0;
$past_time=0;
foreach($input as $key => $value){
  $current_num++;
  $past_time+=(intval($value)-intval($current_pos));
  if((isset($input[$key]) && isset($input[$key-1]) && ($input[$key] == $input[$key-1]))|| (isset($input[$key+1]) && isset($input[$key]) && ($input[$key] == $input[$key+1]))){
    $current_pos = 0;
  }else{
    $current_pos=$value;
  }
  if($current_num == $K){
    break;
  }
}

echo $past_time;