| 123456789 | func complexNumberMultiply(a string, b string) string {	s1 := strings.Split(a, "+")	s2 := strings.Split(b, "+")	a1, _ := strconv.Atoi(s1[0])	a2, _ := strconv.Atoi(s1[1][:len(s1[1])-1])	b1, _ := strconv.Atoi(s2[0])	b2, _ := strconv.Atoi(s2[1][:len(s2[1])-1])	return fmt.Sprintf("%d+%di", a1*b1-a2*b2, a1*b2+a2*b1)}
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