output_description: Print the minimum time required to light K candles.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N K
      x_1 x_2 ... x_N
attempt: # 2019/05/10
  # AtCoder Beginner Contest 107 - C
  
  # Input
  n, k = map(int, input().split())
  x = list(map(int, input().split()))
  
  # Init
  acdist = list()
  # acdist.append(0) # Distance from x[0]
  for i in range(n):
      wx = x[i] - min(x[0], 0)
      acdist.append(wx)
  
  mindist = 10**10
  eflg = False
  
  if x[0] >= 0:
      mindist = x[k - 1]
      eflg = True
  elif x[n - 1] <= 0:
      mindist = abs(x[n - k])
      eflg = True
  
  for i in range(n - k + 1):
      if eflg == True:
          break
      sidx = i
      eidx = i + k - 1
      if (x[eidx] < 0 and eidx < n - 1) or (x[sidx] > 0 and sidx > 0):
          continue
      else:
          # 折り返してゴールまで
          dist = acdist[eidx] - acdist[sidx]
          # 0からSidxまでの距離とEidxまでの距離の小さい方を足す
          dist += min(0 - x[sidx], x[eidx] - 0)
          if dist < mindist:
              mindist = dist
  
  # Output
  print(mindist)
  
problem_description: 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.
samples: [{"input": "5 3\n    -30 -10 10 20 50", "output": "40\n    \n\nHe should move and light candles as follows:\n\n  * Move from coordinate 0 to -10.\n  * Light the second candle from the left.\n  * Move from coordinate -10 to 10.\n  * Light the third candle from the left.\n  * Move from coordinate 10 to 20.\n  * Light the fourth candle from the left.\n\n* * *"}, {"input": "3 2\n    10 20 30", "output": "20\n    \n\n* * *"}, {"input": "1 1\n    0", "output": "0\n    \n\n  * There may be a candle placed at coordinate 0.\n\n* * *"}, {"input": "8 5\n    -9 -7 -4 -3 1 2 3 4", "output": "10"}]