#include <iostream>
using namespace std;

class A {
public:
    virtual void foo(){ cout<<"A"; }
};

class B: public virtual A {
public:
    virtual void foo(){ cout<<"B"; }
};

class C: public virtual A {};
class D: public B, public C {};

int main(void) {
    D d;
    C &c = d;
    c.foo();
    return 0;
}