### Problem Statement

There are N candles placed on a number line. The i-th candle from the left is placed on coordinate xi. Here, x1 < x2 < ... < xN 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
• xi is an integer
• |xi| ≤ 108
• x1 < x2 < ... < xN

### 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.

```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.

```3 2
10 20 30
```

`20`

```1 1
0
```

`0`

### Sample Input 4

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

`10`

### Submitting .cpp to 'candles'

Time Limit: 2 Seconds
Memory Limit: 1024MB