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 Kotlin (1.0.0) (judge verdict: Accepted)

fun main(args: Array<String>) {
    var (N, K) = readLine()!!.split(" ").map(String::toInt)
    val xx = readLine()!!.split(" ").map(String::toInt)
    var pos = mutableListOf<Int>()
    var neg = mutableListOf<Int>()
    for (x in xx) {
        when {
            x == 0 -> K--
            x > 0 -> pos.add(x)
            else -> neg.add(-x)
        }
    }
    if (K == 0) {
        println(0)
        return
    }
    neg.reverse()
    var ans = 1 shl 29
    for (i in 0 until pos.size) {
        val d = pos[i]
        val rest = K - (i + 1)
        if (rest < 0) break
        if (rest == 0) ans = Math.min(ans, d)
        else if (rest <= neg.size) {
            ans = Math.min(ans, d * 2 + neg[rest-1])
        }
    }
    var tmp = pos; pos = neg; neg = tmp;
    for (i in 0 until pos.size) {
        val d = pos[i]
        val rest = K - (i + 1)
        if (rest < 0) break
        if (rest == 0) ans = Math.min(ans, d)
        else if (rest <= neg.size) {
            ans = Math.min(ans, d * 2 + neg[rest-1])
        }
    }
    println(ans)
}