class Solution:
    def complexNumberMultiply(self, num1: str, num2: str) -> str:
        a, b = map(int, num1[:-1].split('+'))
        c, d = map(int, num2[:-1].split('+'))
        real = a*c - b*d
        imag = a*d + b*c
        return f"{real}+{imag}i"
