output_description: For each dataset, output a line containing the amount of ink consumed in
  printing the histogram.
  
  One unit of ink is necessary to paint one highest bar black. Assume that 0.01
  units of ink per histogram is consumed for various purposes except for
  painting bars such as drawing lines and characters (see Figure 1). For
  instance, the amount of ink consumed in printing the histogram in Figure 1 is:
  
  ![](https://judgeapi.u-aizu.ac.jp/resources/images/IMAGE1_greyarea2)
  
  Each output value should be in a decimal fraction and may have an error less
  than 10-5 .
input_description: The input consists of multiple datasets, each of which contains integers and
  specifies a value table and intervals for the histogram generator, in the
  following format.
  
  _n_ _w_  
  _v 1_  
  _v 2_  
  .  
  .  
  _v n_  
  
  _n_ is the total number of value occurrences for the histogram, and each of
  the _n_ lines following the first line contains a single value. Note that the
  same value may possibly occur multiple times.
  
  _w_ is the interval width. A value _v_ is in the first (i.e. leftmost)
  interval if 0 ≤ _v_ < _w_ , the second one if _w_ ≤ _v_ < 2 _w_ , and so on.
  Note that the interval from 0 (inclusive) to _w_ (exclusive) should be
  regarded as the leftmost even if no values occur in this interval. The last
  (i.e. rightmost) interval is the one that includes the largest value in the
  dataset.
  
  You may assume the following.
  
  1 ≤ _n_ ≤ 100  
  10 ≤ _w_ ≤ 50  
  0 ≤ _v i_ ≤ 100 for 1 ≤ i ≤ _n_  
  
  You can also assume that the maximum value is no less than _w_. This means
  that the histogram has more than one interval. The end of the input is
  indicated by a line containing two zeros.
attempt: if __name__ == "__main__":
      print("hello")
  
problem_description: A: Grey Area
  
  Dr. Grey is a data analyst, who visualizes various aspects of data received
  from all over the world everyday. He is extremely good at sophisticated
  visualization tools, but yet his favorite is a simple self-made histogram
  generator.
  
  Figure 1 is an example of histogram automatically produced by his histogram.
  
  ![](https://judgeapi.u-aizu.ac.jp/resources/images/IMAGE1_greyarea1)
  
  A histogram is a visual display of frequencies of value occurrences as bars.
  In this example, values in the interval 0-9 occur five times, those in the
  interval 10-19 occur three times, and 20-29 and 30-39 once each.
  
  Dr. Grey’s histogram generator is a simple tool. First, the height of the
  histogram is fixed, that is, the height of the highest bar is always the same
  and those of the others are automatically adjusted proportionately. Second,
  the widths of bars are also fixed. It can only produce a histogram of uniform
  intervals, that is, each interval of a histogram should have the same width
  (10 in the above example). Finally, the bar for each interval is painted in a
  grey color, where the colors of the leftmost and the rightmost intervals are
  black and white, respectively, and the darkness of bars monotonically
  decreases at the same rate from left to right. For instance, in Figure 1, the
  darkness levels of the four bars are 1, 2/3, 1/3, and 0, respectively.
  
  In this problem, you are requested to estimate ink consumption when printing a
  histogram on paper. The amount of ink necessary to draw a bar is proportional
  to both its area and darkness.
samples: [{"input": "50\n    100\n    0\n    100\n    3 50\n    100\n    100\n    50\n    10 10\n    1\n    2\n    3\n    4\n    5\n    16\n    17\n    18\n    29\n    30\n    0 0", "output": ".51\n    0.26\n    1.4766666666666667"}]