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 Java8 (OpenJDK 1.8.0) (judge verdict: Runtime Error)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

  public static void main(String[] args) {
   
    new Main().run();
  }

  public void run() {
    
    try(BufferedReader in = new BufferedReader(new InputStreamReader(System.in))) {

      String[] lines = in.readLine().split(" ");
      int n = Integer.parseInt(lines[0]);
      int k = Integer.parseInt(lines[1]);

      String line = in.readLine();
      int offset=0,next=0;
      char regx = ' ';
      long[] ax = new long[n];
      for(int i=0; i<n; i++) {
        if((next = line.indexOf(regx,offset)) == -1)
          next = line.length();
        ax[i] = Integer.parseInt(line.substring(offset, next));
        offset = next + 1;
      }

      long min = Long.MAX_VALUE;
      for(int i=0; i<n-k+1; i++) {
        long pos = 0, cost = 0;
        for(int j=i; j<k+1; j++) {
          cost += Math.abs(pos - ax[j]);
          if(cost > min) break;
          pos = ax[j];
        }

        if(min > cost) min = cost;
      }

      if(min == Long.MAX_VALUE) min = 0;

      System.out.println(min);
    }
    catch(IOException e) {
      System.out.println(e);
    }
  }
}