#!/usr/bin/env ruby

require 'optimist'

conf = Optimist::options do
  banner "cma < <one number per line>"
  opt :round, "Number of digits after decimal point.", :type => :int, :default => -1
end

cma = 0.0
i = 0
while line = STDIN.gets
  x = line.to_f
  cma = cma + ((x - cma)/(i+1))
  i +=1
  if conf[:round] >= 0
    puts cma.round conf[:round]
  else
    puts cma
  end
  STDOUT.flush
end