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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
 
 
 
int main() {
    int n,k,x[200000],y,border = 200000;
    long long an = 9000000000000000000;
 
    scanf("%d %d",&n,&k);
    for(y=0;y<n;y++){
        scanf("%d",&x[y]);
        if(x[y] > 0 && border == 200000) border=y;
    }
    k--;
 
    for(y=0;y<n;y++){
        //if(y+k==n) break;
        //if(y+k != border-1 && x[y+k] < 0 || y != border && 0 < x[y]) break;
 
        if(y == border && x[y+k] < an) an = x[y+k];
        else if(y+k == border-1 && -1*x[y] < an) an = -1*x[y];
        else if(y == border || y+k == border-1)  break;
        else if(-2*x[y]+x[y+k] < -1*x[y]+2*x[y+k] && -2*x[y]+x[y+k] < an) an = -2*x[y]+x[y+k];
        else if(-1*x[y]+2*x[y+k] < an) an = -1*x[y]+2*x[y+k];
    }
    printf("%lld\n",an);
 
 
 
 
 
    return 0;
}