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-----
5 3
-30 -10 10 20 50

-----Sample Output-----
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.

见题面

见题面