output_description: For each data set, output the total sales quantity in one line.
input_description: Input file contains several data sets. A single data set has following format:
  
      
      
      _K_
      _c_ 1 _c_ 2 ... _c_ _K_ ×(_K_ -1)/2
      
  
  _K_ is an integer that denotes how many kinds of cakes are sold. _c i_ is an
  integer that denotes a number written on the card.
  
  The end of input is denoted by a case where _K_ = 0. You should output nothing
  for this case.
attempt: while True:
      K = int(input())
      if K == 0:
          break
      else:
          po = [int(i) for i in input().split()]
          print(sum(po) / (K - 1))
  
problem_description: I: A Piece of Cake
  
  In the city, there are two pastry shops. One shop was very popular because its
  cakes are pretty tasty. However, there was a man who is displeased at the
  shop. He was an owner of another shop. Although cause of his shop's
  unpopularity is incredibly awful taste of its cakes, he never improved it. He
  was just growing hate, ill, envy, and jealousy.
  
  Finally, he decided to vandalize the rival.
  
  His vandalize is to mess up sales record of cakes. The rival shop sells _K_
  kinds of cakes and sales quantity is recorded for each kind. He calculates sum
  of sales quantities for all pairs of cakes. Getting _K_(_K_ -1)/2 numbers,
  then he rearranges them randomly, and replace an original sales record with
  them.
  
  An owner of the rival shop is bothered. Could you write, at least, a program
  that finds total sales quantity of all cakes for the pitiful owner?
samples: [{"input": "2\n    3\n    5 4 3\n    0", "output": "6"}]