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: N, K = map(int, input().split())
  x = list(map(int, input().split()))
  
  cnt = 0
  seek = 0
  
  # 左から原点をまたぐ場合
  if x[0] <= 0 and 0 <= x[N - 1]:
      # 左に長い場合
      if abs(x[0]) >= abs(x[N - 1]):
          for i in range(x[N - 1] + 1):
  
              if i in x:
                  cnt += 1
                  if cnt == K:
                      print(i)
                      exit()
              seek = abs(i)
  
          seek = seek * 2
  
          for i in range(0, x[0] - 1, -1):
              seek += 1
              if i in x:
                  cnt += 1
                  if cnt == K:
                      print(seek)
                      exit()
  
      # 右に長い場合
      else:
  
          for i in range(0, x[0] - 1, -1):
              print(i)
              if i in x:
                  cnt += 1
                  print(cnt)
                  if cnt == K:
                      print(i)
                      exit()
              seek = abs(i)
  
          seek = seek * 2
  
          for i in range(x[N - 1] + 1):
              seek += 1
              if i in x:
                  cnt += 1
                  if cnt == K:
                      print(seek)
                      exit()
  
  
  # 原点よりすべて正
  elif x[0] >= 0 and 0 < x[N - 1]:
      for i in range(x[N - 1]):
          if i in x:
              cnt += 1
              if cnt == K:
                  print(i)
                  exit()
  
  
  # 原点よりすべて負
  elif x[0] < 0 and 0 >= x[N - 1]:
      for i in range(x[0]):
          if i in x:
              cnt += 1
              if cnt == K:
                  print(i)
                  exit()
  
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"}]