output_description: For each dataset, print the standard deviation in a line. The output should
  not contain an absolute error greater than 10-4.
input_description: The input consists of multiple datasets. Each dataset is given in the
  following format:
  
      
      
      n
      s1 s2 ... sn
      
  
  The input ends with single zero for n.
attempt: N = int(input())
  S = list(map(float, input().split()))
  m = sum(S) / N
  i = 0
  q = 0
  while i < N:
      q = q + (S[i] - m) ** 2
      i = i + 1
  print(q / N)
  
problem_description: Standard Deviation
  
    
  
  You have final scores of an examination for n students. Calculate standard
  deviation of the scores s1, s2 ... sn.
  
  The variance α2 is defined by
  
  α2 = (∑n _i_ =1(s _i_ \- m)2)/n
  
  where m is an average of si. The standard deviation of the scores is the
  square root of their variance.
samples: [{"input": "70 80 100 90 20\n    3\n    80 80 80\n    0", "output": ".85677655\n    0.00000000"}]