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)

import java.io.*;
import java.util.*;
/**
 * @author Rick
 *
 */
public class Main{

	/**
	 * @param args
	 */
	public static void main(String[] args) throws Exception {
		java.io.BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st = new StringTokenizer(br.readLine());
		int N=Integer.parseInt(st.nextToken().trim());
		int K=Integer.parseInt(st.nextToken().trim());
		int[] Candles=new int[N];
		int ZeroPosition= -1;
		boolean findZero=false;
	    st = new StringTokenizer(br.readLine());
		for(int i=0;i<N;i++)
		{
			int candle=Integer.parseInt(st.nextToken().trim());
			Candles[i]=candle;
			if(candle==0)
			{
				findZero = true;
				ZeroPosition = i;	
			}
			else if(i==0 && candle>0)
			{
				ZeroPosition= -1;
			}
			else if(i>0 && candle > 0 &&  Candles[i-1] <0 && ZeroPosition== -1)
			{
				ZeroPosition=i;
			}
		}
		
		if(ZeroPosition== -1)
		{
			if(Candles[0]<0)
			{
				System.out.println(CaclStep(Candles[Candles.length-K],0));
			}
			else
			{
				System.out.println(CaclStep(0,Candles[K-1]));
			}		
		}
		else
		{
			int MinStep=100000000;
			int i=ZeroPosition-K<0 ? 0 : ZeroPosition-K;
			int JudgeK=K;
			if(findZero)
			{
				i=ZeroPosition-K+1 <0 ? 0: ZeroPosition-K+1;
				for(;i<=ZeroPosition+K-1;i++)
				{
					if(i<0)
						continue;
					if(i+K > Candles.length)
						break;
					int Step=CaclStep(Candles[i],Candles[i+K-1]);
					if(MinStep>Step)
						MinStep=Step;				
				}
			}
			else
			{
				for(;i<=N-JudgeK;i++)
				{
					if(i<0)
						continue;
					if(i+K > Candles.length)
						break;
					int Step=CaclStep(Candles[i],Candles[i+K-1]);
					if(MinStep>Step)
						MinStep=Step;				
				}
			}
			System.out.println(MinStep);
		}
	}
	
	private static int CaclStep( int i, int j)
	{
		if(i<0 && j>0)
		{
			if(i*-1 >= j)
				return i*-1 + j*2;
			else
				return i*-2 +j;
		}
		else if(i<0 && j<=0)
		{
			return i*-1;
		}
		else if (i>=0 && j>0)
		{ 
			return j;
		}
		else
		{ 
			return j;
		}
	}
}