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 (Python):
N,  K = map(int, input().split())
candles = list(map(int, input().split()))
ans = float('inf')
for i in range(N - K + 1):
    if candles[i] * candles[i + K - 1] >= 0:
        t = max(abs(candles[i]), abs(candles[i + K - 1]))
    else:
        t = candles[i + K - 1] - candles[i] + min(abs(candles[i]), abs(candles[i + K - 1]))
    ans = min(ans, t)
print(ans)