everything works fine on xcode and i have done what is mentioned in the task exactly the same can anyone help me please

class Person {
    let firstName: String
    let lastName: String

    init(firstName: String, lastName: String) {
        self.firstName = firstName
        self.lastName = lastName
    }

    func getFullName() -> String {
        return "\(firstName) \(lastName)"
    }
}
class Doctor : Person {
    override init(firstName: String, lastName: String) {
        super.init(firstName: firstName , lastName: lastName)

    }
    override func getFullName() -> String {
        return " Dr.\(lastName)"
    }
}
Person.init(firstName : "Sam" , LastName : "Smith" ).getFullName()
 let  someDoctor = Doctor.init(firstName: "Sam" , lastName: "Smith").getFullName()