Наследование

#include <iostream>
#include <string>
using namespace std;
 
class Human{
string firstname;
string name;
string lastname;
int birthday;
int birthmonth;
int birthyear;
string stat;
public:
    Human(){
    string firstname = "";
    string name = "";
    string lastname = "";
    int birthday = 0;
    int birthmonth = 0;
    int birthyear = 0;
    string stat = "";
    }
  void input(){
  cout<<"Enter firstname: ";
  cin>>firstname;
  cout<<"Enter name: ";
  cin>>name;
  cout<<"Enter lasstname: ";
  cin>>lastname;
  cout<<"Enter birthday: ";
  cin>>birthday;
  cout<<"Enter birthmonth: ";
  cin>>birthmonth;
  cout<<"Enter birthyear: ";
  cin>>birthyear;
  cout<<"Enter stat: ";
  cin>>stat;
  }
  void show(){
  cout<<firstname<<endl<<name<<endl<<lastname<<endl<<birthday<<endl<<birthmonth<<endl<<birthyear<<endl<<stat<<endl;
  }
};
 
class Employee: public Human{
int id;
int day;
int month;
int year;
string posada;
public:
    Employee():Human(){
    id = 0;
    day = 0;
    month = 0;
    year = 0;
    posada = "";
    }
    ~Employee(){
    }
    void input(){
    cout<<"Enter id: ";
    cin>>id;
 
    cout<<"Enter day: ";
    cin>>day;
 
    cout<<"Enter month: ";
    cin>>month;
 
    cout<<"Enter year: ";
    cin>>year;
 
    cout<<"Enter posada: ";
    cin>>posada;
    }
    void show(){
    cout<<id<<endl<<day<<endl<<month<<endl<<year<<endl<<posada;
    }
};
int main(){
Employee a;
Human b;
b.input();
a.input();
b.show();
a.show();
}