class ComplexNumber(object):
    def __init__(self, a=0,b=0):
        self.a=a
        self.b=b
    def __str__(self):
     return str(self.a)+"+"+str(self.b)+"i"

    def conjugate(self):
        return ComplexNumber(self.a,-1*self.b)

    def add(self,N):
        return ComplexNumber(self.a+N.a, self.b+N.b)

    def substract(self,N):
        real=self.a-N.a
        imaginary=self.b-N.b
        return ComplexNumber(real,imaginary)


c1=ComplexNumber(2,4)
c2=ComplexNumber(-9,20)

print"c1:",c1
print"c1.conjugate()",c1.conjugate()
print"c2:", c2
print"c2.conjugate()",c2.conjugate()

print"c1+c2:",c1.add(c2)
print"c1+c1.conjugate()", c1.add(c1.conjugate())

print"c1-c2:",c1.substract(c2)