class Base
{
  int data;
public:
  Base(int D)
  {
    data = D;
  }
};    class B1:virtual public Base
{
  int data;
public:
  B1(int D):Base(D)
  {
    data = D;
  }
};    class B2:virtual public Base
{
  int data;
public:
  B2(int D):Base(D)
  {
    data = D;
  }
};    class C:public B1,public B2
{
  int data;
public:
  C(int D):B1(D),B2(D)  //  這裏會有錯誤 Cannot find default constructor to
                        //   initialize base class 'Base'
  {
    data = D;
  }
};    

class C:public B1,public B2
{
  int data;
public:
  C(int D):Base(D),B1(D),B2(D)  // Virtual Class 再呼叫一次
  {
    data = D;
  }
};