welcome = "Введите a, b, c: "
print(welcome)
a = float(input("a = "))
b = float(input("b = "))
c = float(input("c = "))
d = (b * b) - 4 * a * c
print('D = ', d)
if d > 0:
    import math
    x1 = (-b + math.sqrt(d)) / (2 * a)
    x2 = (-b - math.sqrt(d)) / (2 * a)
    print("x1 = ", x1, "x2 = ", x2)
elif d == 0:
    x = -b / (2 * a)
    print("x = ", x)
else:
    print("Корней нет")