修改下面的4个类，添加析构函数，在析构函数中输出各私有数据成员的值。并分析结果。
#include <iostream>
using namespace std;
class B1
{
public:
    B1(int i)
    {
        b1 = i;
        cout<<"构造函数 B1."<<b1<<endl; }
    void print() { cout<<b1<<endl; }
private:
    int b1;
};

class B2
{
public:
    B2(int i)
    {
        b2 = i;
        cout<<"构造函数 B2."<<b2<<endl; }
    void print() { cout<<b2<<endl;}
private:
    int b2;
};

class B3
{
public:
    B3(int i)
    {
        b3 = i;
        cout<<"构造函数 B3."<<b3<<endl; }
    int getb3() { return b3; }
private:
    int b3;
};
class A : public B2, public B1
{
public:
    A(int i, int j, int k, int l):B1(i), B2(j), bb(k)
    {
        a = l;
        cout<<"构造函数 A."<<a<<endl; }
    void print()
    {
        B1::print();
        B2::print();
        cout<<a<<endl;}
private:
    int a;
    B3 bb;
};

void main()
{
    A aa(1, 2, 3, 4);
    aa.print();
}

楼上那位高手,小弟十分感谢你的解答,谢谢