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.*;
 
public class Main {
 
 
    public static int main(String[] args)throws Exception{
        Scanner sc = new Scanner(System.in);
        int n= sc.nextInt();
        int k = sc.nextInt();
        int[] candle = new int[n];
        for (int i = 0; i < n;i++)
            candle[i] = sc.nextInt();
        int index =0;
        for (; index < n;index++)
            if (candle[index]>= 0)
                break;
        int min =Integer.MAX_VALUE;
        if (index == n)
            return -candle[n-k];
        for(int i =0; i< k; i++){
            int l = abs(i,index-1,  candle, -1);
            int r = abs(k-i,index+1,  candle, 1);
            if(r==0 || l == 0)
                min = Math.min(min, Math.max(l,r));
            else {
                int t = l< r + candle[index]? l*2 + r : l+ r*2;
                min = Math.min(min, t);
            }
 
        }
        return min;
 
    }
 
    public static int abs(int left, int index, int[] candle, int dir){
        if (index < 0 || index >= candle.length)
            return 0;
        if (left== 0)
            return 0;
        if (left == 1)
            return Math.abs(candle[index]);
        if (dir< 0){
            return abs(left-1, index-1, candle,dir);
        }
        else{
            return abs(left-1, index+1, candle,dir);
        }
    }
 
 
 
}