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 Python (3.8.2) (judge verdict: Wrong Answer)

n, k = map(int, input().split())
x = list(map(int, input().split()))

inf = 10**12
z = len(x) - 1
for i in range(len(x)):
    if x[i] >= 0:
        z = i
        break

r = [inf] * (n - z)
l = [inf] * z

for i in range(n-z):
    r[i] = x[z+i]

for i in range(z):
    l[i] = abs(x[z-i-1])

# 左からすべて取る場合
tl = inf
if len(l) < k:
    tl = inf
else:
    tl = l[k-1]

# 右からすべて取る場合
tr = inf
if len(r) < k:
    tr = inf
else:
    tr = r[k-1]    

# 両方から取る場合
# 右からi個取る
t_arr = []
for i in range(1,k):
    if i-1 >= len(r):
        pass
    else:
        if k-i-1 >= len(l):
            pass
        else:
            t1 = r[i-1]
            t2 = l[k-i-1]
            t_arr.append(t1*2 + t2*2 - max(t1,t2))
tc = inf
if len(t_arr) != 0:
    tc = min(t_arr)
else:
    tc = inf
print(min(abs(tl),tr,tc))