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.util.*;
import java.lang.*;


public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int k = sc.nextInt();
        int x[] = new int[n];
        int a = -1;
        int origin = -1;
        for (int i = 0; i < n; i++) {
            x[i] = sc.nextInt();
            if (x[i] < 0) {
                a = i;
            } else if (x[i] == 0) {
                origin = i;
            }
        }
        int sum = 0;
        if (a == -1) {
            if (origin == -1) {
                sum = x[k - 1];
            } else {
                if (k == 1) {
                    sum = 0;
                } else {
                    sum = x[k - 2];
                }
            }
        } else {
            int min = 1000000000;
            for (int i = 0; i + k - 1 < n; i++) {
                min = Math.min(min, Math.min(2 * Math.abs(x[i]) + Math.abs(x[i + k - 1]), Math.abs(x[i]) + 2 * Math.abs(x[i + k - 1])));
            }
            sum = min;
        }
        System.out.println(sum);
    }
}