class Solution {
public:
string complexNumberMultiply(string num1, string num2) {
int a, b, c, d;
sscanf(num1.c_str(), "%d+%di", &a, &b);
sscanf(num2.c_str(), "%d+%di", &c, &d);
return to_string(a * c - b * d) + "+" + to_string(a * d + b * c) + "i";
}
};