Помогите найти ошибку при множественном наследовании

#include <iostream>
 
using namespace std;
 
class B1 
{protected:;
 
public:int b1;
B1(int a):b1(a){}
void showB1()   {
cout << "B1 = " << b1 << endl;
}
};
class B2
{public:
int b2;
B2(int b):b2(b){}
void showB2()   {
cout << "B2 = " << b2 << endl;
}
};
class D1:protected B1,public B2
{public:
int d1;
D1(int c,int a,int b):B1(a),B2(b),d1(c){}
void showD1()   {
cout << "D1 = " << d1 << endl;
showB1();
showB2();
}
};
class B3
{protected:
int b3;
public:
B3(int d):b3(d){}
void showB3()   {
cout << "B3 = " << b3 << endl;
}
};
 
 
class D2:public D1,protected B3
{public:
int d2;
D2(int a , int b, int c,int d,int g):D1(a,b,c),B3(d),d2(g){}
 
void showD2()   {
cout << "D2 = " << d2 << endl;
 
showD1();
showB3();
}
};
class D3:public D2
{public:
int d3;
D3(int a , int b, int c,int d,int g,int e):D2(a,b,c,d,g),d3(e){}
void showD3()   {
cout << "D3 = " << d3 << endl;
 
showD2();
 
}
};
int main () {
D3 elemD3(100, 200, 300, 400 ,500, 600);
   elemD3.showD3();
 
 
 
 
system("pause");
return 0;
 
}