candles

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, x₁ < x₂ < ... < 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 amount of time to light K candles.

Constraints

• 1 ≤ N ≤ 10⁵
• 1 ≤ K ≤ N
• x_i is an integer
• |x_i| ≤ 10⁸
• x₁ < x₂ < ... < x_N

Input

Input is given from Standard Input in the following format:

N K
x1 x2 ... xN

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

Sample Input 4

8 5
-9 -7 -4 -3 1 2 3 4

Sample Output 4

10