Constructor and Destructor of derived Class

Example of Constructor and Destructor of derived Class:

#include <iostream>

using namespace std;

class BASE{
    public:
        BASE(int x, int y, int z);
        ~BASE();
        void doit();
        int a;
    protected:
        int b;
        string Im;
    private:
        int c;
};



BASE::BASE(int x, int y, int z)
:a(x), b(y), c(z){
    Im = "Base Class";
}

BASE::~BASE(){
    cout << "BASE's destructor! " << Im << endl;
}

void BASE::doit(){
    cout << "BASE::doit()" << endl;
    cout << a << endl;
    cout << b << endl;
    cout << c << endl;
}

class DERIVED:public BASE{
     public:
        DERIVED(int x, int y, int z, int w);
        ~DERIVED();
        void doit();
    private:
        int d;
};

DERIVED::DERIVED(int x, int y, int z, int w)
:BASE(x, y, z), d(w){
    Im = "Derived Class";
}

DERIVED::~DERIVED(){
    cout << "DERIVED's destructor! " << Im << endl;
}

void DERIVED::doit(){
    cout << "DERIVED::doit()" << endl;
    BASE::doit();
    cout << d << endl;
}

int main()
{

    BASE base(1, 2, 3);
    base.doit();
    DERIVED derived(4, 5, 6, 7);
    derived.doit();
    return 0;
}