import cmath

import math

import sys

def get_float(msg,allow_zero):

 x = None

 while x is None:

  try:

   x = float(input(msg))

   if not allow_zero and abs(x) < sys.float_info.epsilon:    #float_info.epsilon为接近0值的浮点数，因计算机浮点数只能无限接近0

    print("zero is not allowed")

    x = None

  except ValueError as err:

   print(err)

 return x

 

print("ax2 + bx +c = 0")

a = get_float("enter a:",False)

b = get_float("enter b:",True)

c = get_float("enter c:",True)

x1 = None

x2 = None

discriminant = (b ** 2) - (4*a*c)

if discriminant == 0:

 x1 = -(b/(2*a))

 print(x1)

else:

 if discriminant > 0: 

  root = math.sqrt(discriminant)

 else:

  root = cmath.sqrt(discriminant)   #cmath为复数形式

 x1 = (-b+root)/(2*a)

 x2 = (-b-root)/(2*a)

 print(x1)

 print(x2)