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: Wrong Answer)

//package main;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;

public class Main{
	
	
	
	private static boolean isPrint = false;
	public static void main(String[] args) throws Exception {
		/*BufferedReader br = new BufferedReader(
				new InputStreamReader(Main.class.getResourceAsStream("/data.txt")));*/
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String[] systemInLine = br.readLine().split(" ");
		//蜡烛总数 
		int candleCount = Integer.parseInt(systemInLine[0]);
		//点燃总数 
		int burning = Integer.parseInt(systemInLine[1]);
		showMessage("蜡烛总数:"+candleCount+",点燃总数:"+burning);
		systemInLine = br.readLine().split(" ");
		List<Cd> list = new ArrayList<>(candleCount);
		for (int i = 0; i < candleCount; i++) {
			list.add(new Cd(i+1, Integer.parseInt(systemInLine[i])));
		}
		showMessage(list);
		int left = Integer.MIN_VALUE;
		int right = Integer.MAX_VALUE;
		int sum = Integer.MAX_VALUE;
		for (int i = 0; i < systemInLine.length&&i+burning-1<systemInLine.length; i++) {
			left = list.get(i).getAbsValue();
			right = list.get(i+burning-1).getAbsValue();
			sum =Math.min(Math.min(left*2+right, left+right*2),sum);
		}
		System.out.println(sum);
	}
	/**
	 * 前m个中点燃n个的最少路程
	 * @param m
	 * @param n
	 * @return
	 */
	public static int burningCandle(int m,int n) {
		return
				0;
	}
	public static void showMessage(Object message) {
		if(isPrint) {
			System.out.println(message);
		}
	}
}
class Cd{
	//顺序编号
	private int seq;
	//坐标
	private int index;
	//距离0点距离
	private int absValue;
	public int getSeq() {
		return seq;
	}
	public void setSeq(int seq) {
		this.seq = seq;
	}
	public int getIndex() {
		return index;
	}
	public void setIndex(int index) {
		this.index = index;
	}
	public int getAbsValue() {
		return absValue;
	}
	/*public void setAbsValue(int absValue) {
		this.absValue = absValue;
	}*/
	public Cd(int seq, int index) {
		super();
		this.seq = seq;
		this.index = index;
		this.absValue = Math.abs(index);
	}
	@Override
	public String toString() {
		return "Cd [seq=" + seq + ", index=" + index + ", absValue=" + absValue + "]";
	}
	
	
}