def newton(xn, q)
  if (xn ** 3 - q).abs < q * 10 ** -5
    return xn
  else
    newton(xn - (xn ** 3 - q) / (3 * xn ** 2), q)
  end
end
def main(input = STDIN)
  while (q = input.gets.to_i) != -1
    puts newton(1.0, q)
  end
end
main