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.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        final Scanner sc = new Scanner(System.in);
        final int N = sc.nextInt();
        final int K = sc.nextInt();

        final List<Long> posiArray = new ArrayList<Long>();
        final List<Long> negaArray = new ArrayList<Long>();
        long input;
        int count = 0;
        for (int i = 0; i < N; i++)
        {
            input = sc.nextInt();
            if (input < 0)
            {
                negaArray.add(input);
            } else if (input > 0)
            {
                posiArray.add(input);
            } else
            {
                count++;
            }

        }
        int posiIndex = 0;
        int negaIndex = negaArray.size() - 1;
        long distance = 0;
        final boolean beforeNumNegative = false;
        for (int i = 0; i < N; i++)
        {
            if (posiArray.size() == 0 && negaArray.size() == 0)
            {
                distance = 0;
                break;
            } else if (posiArray.size() == 0)
            {
                distance = -negaArray.get(K - 1);
                break;
            } else if (negaArray.size() == 0)
            {
                distance = posiArray.get(K - 1);
                break;
            } else if (posiIndex < posiArray.size() && posiArray.get(posiIndex) < -2 * negaArray.get(negaIndex))
            {
                posiIndex++;
            } else if (negaIndex < negaArray.size() && posiArray.get(posiIndex) > -2 * negaArray.get(negaIndex))
            {
                negaIndex--;
            } else if (posiArray.get(posiIndex) == -2 * negaArray.get(negaIndex) && posiIndex < posiArray.size()
                    && negaIndex < negaArray.size())
            {
                if (beforeNumNegative)
                {
                    negaIndex--;
                } else
                {
                    posiIndex++;
                }
            }
            count++;
            if (count == K)
            {
                final long posiDis = posiArray.get(posiIndex - 1);
                final long negaDis = negaArray.get(negaIndex + 1);
                if (posiDis - 2 * negaDis > 2 * posiDis - negaDis)
                {
                    distance = 2 * posiDis - negaDis;
                } else
                {
                    distance = posiDis - 2 * negaDis;
                }
                break;
            }
        }
        System.out.println(distance);
    }
}