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.

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.

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

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

见题面 Input 部分

见题面 Output 部分