#include <iostream>

 using namespace std;

 class A {

 public:

     A();

     ~A();

 };

 A::A() { cout << "A construction" << endl; }

 A::~A() { cout << "A destruction" << endl; }

 class B : public A {

 public:

     B();

     ~B();

 };

 B::B() { cout << "B construction" << endl; }

 B::~B() { cout << "B destruction" << endl; }

 class C : public B {

 public:

     C();

     ~C();

 };

 C::C() { cout << "C construction" << endl; }

 C::~C() { cout << "C destruction" << endl; }

 int main()

 {

     std::cout << "Hello World!\n";

     C c;    //先执行A的构造函数然后是B,最后为C. 析构函数则相反

     return ;

 }