Quadratic equation in Boo

A = int.Parse(prompt("A = "))
if A==0 :
    print "Not a quadratic equation."
    return
B = int.Parse(prompt("B = "))
C = int.Parse(prompt("C = "))
D = B*B-4*A*C
if D==0 :
    x = -0.5*B/A
    print "x = ${x}"
    return
if D>0 :
    x1 = 0.5*(-B-System.Math.Sqrt(D))/A
    x2 = 0.5*(-B+System.Math.Sqrt(D))/A
    print "x1 = ${x1}"
    print "x2 = ${x2}"
else :
    r = -0.5*B/A
    i = 0.5*System.Math.Sqrt(-D)/System.Math.Abs(A)
    print "x1 = (${r},${i})"
    print "x2 = (${r},-${i})"