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.Scanner;
public class Main {

	public static void main(String args[]) throws Exception {

		int N = 0;
		int K = 0;
		int X;
		int lOCATION[] = null;
		int ans = (int) (2*Math.pow(10, 15));

		Scanner sc = new Scanner(System.in);
		N = sc.nextInt();

		if (N >= 1 && N <= (int) Math.pow(10, 5)) {
			lOCATION = new int[N];
			K = sc.nextInt();
			sc.nextLine();
			if (K >= 1 && K <= N) {
				for (int i = 0; i <= N-1; i++) {
					X = sc.nextInt();
					if (Math.abs(X) >= 1 && Math.abs(X) <= Math.pow(10, 8)) {
						lOCATION[i] = X;
						// if (Y >= 1 && Y <= (int)Math.pow(10,9)) {

					}

				}

			}

		}
		for (int i = 0; i + K - 1 <= N-1; i++) {
			int l = i;
			int r = i + K - 1;
			ans = Math.min(ans, lOCATION[r] - lOCATION[l] + Math.min(Math.abs(lOCATION[l]), Math.abs(lOCATION[r])));
			System.out.println("ans="+ans);
		}

	}
}