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) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		int K = sc.nextInt();
		int[] x = new int[N];
		int[] absx = new int[N];
		for(int i = 0;i < N;++i) {
			x[i] = sc.nextInt();
			absx[i] = Math.abs(x[i]);
		}
		sc.close();
		
		int p0 = -1;
		for(int i = 0;i < N;++i) {
			if(x[i] >= 0) {
				p0 = i;
				break;
			}
		}
		if(p0 == -1)
			p0 = N-1;
		
		int ncount = 0;
		int pcount = 0;
		for(int i = 0;i < K;++i) {
			if(p0 - ncount == 0) {
				pcount++;
			}else if(p0 + pcount == N-1) {
				ncount++;
			}else if(absx[p0 - ncount - 1] > absx[p0 + pcount]) {
				//System.out.println("p" + absx[p0 - ncount - 1] + ":" + absx[p0 + pcount]);
				pcount++;
			}else {
				//System.out.println("n" + absx[p0 - ncount - 1] + ":" + absx[p0 + pcount]);
				ncount++;
			}
		}
		//System.out.println(ncount + ":" + pcount);
		
		int ans = 0;
		if(pcount == 0) {
			ans = absx[p0-ncount];
		}else if(ncount == 0) {
			ans = absx[p0+pcount-1];
		}else if(absx[p0 - ncount] > absx[p0 + pcount - 1]) {
			ans = absx[p0+pcount - 1] * 2 + absx[p0-ncount];
		}else {
			ans = absx[p0-ncount] * 2 + absx[p0+pcount - 1];
		}
		
		if(p0 + K < N)
			if(ans > absx[p0 + K - 1])
				ans = absx[p0+K-1];
		if(p0 - K >= 0)
			if(ans > absx[p0 - K])
				ans = absx[p0 - K];
		System.out.println(ans);
	}
}