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 void 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){
            System.out.println(-candle[n-k]);
            return;
        }
//        int limit = k < index ? k: index;
        for(int i =0; i<= index; i++){
            int l = i ==0 ? 0 : Math.abs(candle[index -i]);
            int r = i == k-1? 0: Math.abs(candle[index+k-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);
            }

        }
        System.out.println( min);

    }

}