output_description: Print the maximum possible value of the expected value of the sum of the
  numbers shown.
  
  Your output will be considered correct when its absolute or relative error
  from our answer is at most 10^{-6}.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N K
      p_1 ... p_N
attempt: NK = [int(i) for i in input().split(" ")]
  list1 = [(int(i) + 1) / 2 for i in input().split(" ")]
  Max = 0
  for j in range(NK[0] - NK[1] + 1):
      if Max < sum(list1[j : j + NK[1]]):
          Max = sum(list1[j : j + NK[1]])
  
problem_description: Statement
  
  We have N dice arranged in a line from left to right. The i-th die from the
  left shows p_i numbers from 1 to p_i with equal probability when thrown.
  
  We will choose K adjacent dice, throw each of them independently, and compute
  the sum of the numbers shown. Find the maximum possible value of the expected
  value of this sum.
samples: [{"input": "5 3\n    1 2 2 4 5", "output": "7.000000000000\n    \n\nWhen we throw the third, fourth, and fifth dice from the left, the expected\nvalue of the sum of the numbers shown is 7. This is the maximum value we can\nachieve.\n\n* * *"}, {"input": "4 1\n    6 6 6 6", "output": "3.500000000000\n    \n\nRegardless of which die we choose, the expected value of the number shown is\n3.5.\n\n* * *"}, {"input": "10 4\n    17 13 13 12 15 20 10 13 17 11", "output": "32.000000000000"}]