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 Rust (1.42.0) (judge verdict: Wrong Answer)

use proconio::input;
 
fn main() {
  input! {
    n: usize,
    mut k: usize,
    mut vals: [isize;n]
  }
  
  for (i, v) in vals.iter().enumerate() {
    if v == &0 {
      k -= 1;
      vals.remove(i);
      break;
    }
  }
  
  if k == 0 {
    println!("0");
    return
  }
  
  let mut min = 0;
  let mut last = 0;
  for i in 0..k {
    min += (last - vals[i]).abs();
    last = vals[i];
  }
  
  let mut temp = min;
  for i in k..vals.len() {
    temp -= vals[i-k].abs();
    temp -= (vals[i-k+1] - vals[i-k]).abs();
    temp += vals[i-k+1].abs();
    temp += (vals[i] - last).abs();
    last = vals[i];
    min = std::cmp::min(min, temp);
  }
  
  println!("{}", min);
}