def solve(q)
  x = q.to_f / 2.to_f
  loop do
    p x
    x = x - (x ** 3 - q) / (3 * x ** 2)
    break if (x ** 3 - q).abs < 10 ** -5
  end
  return x
end

loop do
  break if (q = $stdin.gets.to_i) == -1
  p solve(q)
end